Merge pull request #726 from TomHarte/BD-DOS

Implements highly-provisional Byte Drive 500 support for the Oric.

.github/workflows/ccpp.yml

@@ -0,0 +1,22 @@
+name: SDL/Ubuntu
+
+on:
+  push:
+    branches: 
+      - master
+
+  pull_request:
+    branches: 
+      - master
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    
+    steps:
+    - uses: actions/checkout@v1
+    - name: Install dependencies
+      run: sudo apt-get --allow-releaseinfo-change update; sudo apt-get install libsdl2-dev scons
+    - name: Make
+      run: cd OSBindings/SDL; scons

.travis.yml

@@ -1,13 +0,0 @@
-# language: objective-c
-# osx_image: xcode8.2
-# xcode_project: OSBindings/Mac/Clock Signal.xcodeproj
-# xcode_scheme: Clock Signal
-# xcode_sdk: macosx10.12
-
-language: cpp
-before_install:
-	- sudo apt-get install libsdl2-dev
-script: cd OSBindings/SDL && scons
-compiler:
-	- clang
-	- gcc

Analyser/Dynamic/MultiMachine/Implementation/MultiCRTMachine.cpp

@@ -13,7 +13,7 @@
 
 using namespace Analyser::Dynamic;
 
-MultiCRTMachine::MultiCRTMachine(const std::vector<std::unique_ptr<::Machine::DynamicMachine>> &machines, std::mutex &machines_mutex) :
+MultiCRTMachine::MultiCRTMachine(const std::vector<std::unique_ptr<::Machine::DynamicMachine>> &machines, std::recursive_mutex &machines_mutex) :
 	machines_(machines), machines_mutex_(machines_mutex), queues_(machines.size()) {
 	speaker_ = MultiSpeaker::create(machines);
 }
@@ -25,7 +25,7 @@ void MultiCRTMachine::perform_parallel(const std::function<void(::CRTMachine::Ma
 	std::condition_variable condition;
 	std::mutex mutex;
 	{
-		std::lock_guard<std::mutex> machines_lock(machines_mutex_);
+		std::lock_guard<decltype(machines_mutex_)> machines_lock(machines_mutex_);
 		std::lock_guard<std::mutex> lock(mutex);
 		outstanding_machines = machines_.size();
 
@@ -46,29 +46,18 @@ void MultiCRTMachine::perform_parallel(const std::function<void(::CRTMachine::Ma
 }
 
 void MultiCRTMachine::perform_serial(const std::function<void (::CRTMachine::Machine *)> &function) {
-	std::lock_guard<std::mutex> machines_lock(machines_mutex_);
+	std::lock_guard<decltype(machines_mutex_)> machines_lock(machines_mutex_);
 	for(const auto &machine: machines_) {
-		CRTMachine::Machine *crt_machine = machine->crt_machine();
+		CRTMachine::Machine *const crt_machine = machine->crt_machine();
 		if(crt_machine) function(crt_machine);
 	}
 }
 
-void MultiCRTMachine::setup_output(float aspect_ratio) {
-	perform_serial([=](::CRTMachine::Machine *machine) {
-		machine->setup_output(aspect_ratio);
-	});
-}
+void MultiCRTMachine::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
+	scan_target_ = scan_target;
 
-void MultiCRTMachine::close_output() {
-	perform_serial([=](::CRTMachine::Machine *machine) {
-		machine->close_output();
-	});
-}
-
-Outputs::CRT::CRT *MultiCRTMachine::get_crt() {
-	std::lock_guard<std::mutex> machines_lock(machines_mutex_);
-	CRTMachine::Machine *crt_machine = machines_.front()->crt_machine();
-	return crt_machine ? crt_machine->get_crt() : nullptr;
+	CRTMachine::Machine *const crt_machine = machines_.front()->crt_machine();
+	if(crt_machine) crt_machine->set_scan_target(scan_target);
 }
 
 Outputs::Speaker::Speaker *MultiCRTMachine::get_speaker() {
@@ -84,6 +73,14 @@ void MultiCRTMachine::run_for(Time::Seconds duration) {
 }
 
 void MultiCRTMachine::did_change_machine_order() {
+	if(scan_target_) scan_target_->will_change_owner();
+
+	perform_serial([=](::CRTMachine::Machine *machine) {
+		machine->set_scan_target(nullptr);
+	});
+	CRTMachine::Machine *const crt_machine = machines_.front()->crt_machine();
+	if(crt_machine) crt_machine->set_scan_target(scan_target_);
+
 	if(speaker_) {
 		speaker_->set_new_front_machine(machines_.front().get());
 	}

Analyser/Dynamic/MultiMachine/Implementation/MultiCRTMachine.hpp

@@ -31,7 +31,7 @@ namespace Dynamic {
 */
 class MultiCRTMachine: public CRTMachine::Machine {
 	public:
-		MultiCRTMachine(const std::vector<std::unique_ptr<::Machine::DynamicMachine>> &machines, std::mutex &machines_mutex);
+		MultiCRTMachine(const std::vector<std::unique_ptr<::Machine::DynamicMachine>> &machines, std::recursive_mutex &machines_mutex);
 
 		/*!
 			Informs the MultiCRTMachine that the order of machines has changed; the MultiCRTMachine
@@ -53,19 +53,18 @@ class MultiCRTMachine: public CRTMachine::Machine {
 		}
 
 		// Below is the standard CRTMachine::Machine interface; see there for documentation.
-		void setup_output(float aspect_ratio) override;
-		void close_output() override;
-		Outputs::CRT::CRT *get_crt() override;
+		void set_scan_target(Outputs::Display::ScanTarget *scan_target) override;
 		Outputs::Speaker::Speaker *get_speaker() override;
 		void run_for(Time::Seconds duration) override;
 
 	private:
 		void run_for(const Cycles cycles) override {}
 		const std::vector<std::unique_ptr<::Machine::DynamicMachine>> &machines_;
-		std::mutex &machines_mutex_;
+		std::recursive_mutex &machines_mutex_;
 		std::vector<Concurrency::AsyncTaskQueue> queues_;
 		MultiSpeaker *speaker_ = nullptr;
 		Delegate *delegate_ = nullptr;
+		Outputs::Display::ScanTarget *scan_target_ = nullptr;
 
 		/*!
 			Performs a parallel for operation across all machines, performing the supplied

Analyser/Dynamic/MultiMachine/Implementation/MultiJoystickMachine.cpp

@@ -81,6 +81,6 @@ MultiJoystickMachine::MultiJoystickMachine(const std::vector<std::unique_ptr<::M
 	}
 }
 
-std::vector<std::unique_ptr<Inputs::Joystick>> &MultiJoystickMachine::get_joysticks() {
+const std::vector<std::unique_ptr<Inputs::Joystick>> &MultiJoystickMachine::get_joysticks() {
 	return joysticks_;
 }

Analyser/Dynamic/MultiMachine/Implementation/MultiJoystickMachine.hpp

@@ -28,7 +28,7 @@ class MultiJoystickMachine: public JoystickMachine::Machine {
 		MultiJoystickMachine(const std::vector<std::unique_ptr<::Machine::DynamicMachine>> &machines);
 
 		// Below is the standard JoystickMachine::Machine interface; see there for documentation.
-		std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() override;
+		const std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() override;
 
 	private:
 		std::vector<std::unique_ptr<Inputs::Joystick>> joysticks_;

Analyser/Dynamic/MultiMachine/Implementation/MultiKeyboardMachine.cpp

@@ -10,7 +10,8 @@
 
 using namespace Analyser::Dynamic;
 
-MultiKeyboardMachine::MultiKeyboardMachine(const std::vector<std::unique_ptr<::Machine::DynamicMachine>> &machines) {
+MultiKeyboardMachine::MultiKeyboardMachine(const std::vector<std::unique_ptr<::Machine::DynamicMachine>> &machines) :
+	keyboard_(machines_) {
 	for(const auto &machine: machines) {
 		KeyboardMachine::Machine *keyboard_machine = machine->keyboard_machine();
 		if(keyboard_machine) machines_.push_back(keyboard_machine);
@@ -35,9 +36,34 @@ void MultiKeyboardMachine::type_string(const std::string &string) {
 	}
 }
 
-void MultiKeyboardMachine::keyboard_did_change_key(Inputs::Keyboard *keyboard, Inputs::Keyboard::Key key, bool is_pressed) {
+Inputs::Keyboard &MultiKeyboardMachine::get_keyboard() {
+	return keyboard_;
+}
+
+MultiKeyboardMachine::MultiKeyboard::MultiKeyboard(const std::vector<::KeyboardMachine::Machine *> &machines)
+	: machines_(machines) {
 	for(const auto &machine: machines_) {
-		uint16_t mapped_key = machine->get_keyboard_mapper()->mapped_key_for_key(key);
-		if(mapped_key != KeyNotMapped) machine->set_key_state(mapped_key, is_pressed);
+		observed_keys_.insert(machine->get_keyboard().observed_keys().begin(), machine->get_keyboard().observed_keys().end());
+		is_exclusive_ |= machine->get_keyboard().is_exclusive();
 	}
 }
+
+void MultiKeyboardMachine::MultiKeyboard::set_key_pressed(Key key, char value, bool is_pressed) {
+	for(const auto &machine: machines_) {
+		machine->get_keyboard().set_key_pressed(key, value, is_pressed);
+	}
+}
+
+void MultiKeyboardMachine::MultiKeyboard::reset_all_keys() {
+	for(const auto &machine: machines_) {
+		machine->get_keyboard().reset_all_keys();
+	}
+}
+
+const std::set<Inputs::Keyboard::Key> &MultiKeyboardMachine::MultiKeyboard::observed_keys() {
+	return observed_keys_;
+}
+
+bool MultiKeyboardMachine::MultiKeyboard::is_exclusive() {
+	return is_exclusive_;
+}

Analyser/Dynamic/MultiMachine/Implementation/MultiKeyboardMachine.hpp

@@ -25,6 +25,25 @@ namespace Dynamic {
 	order of delivered messages.
 */
 class MultiKeyboardMachine: public KeyboardMachine::Machine {
+	private:
+		std::vector<::KeyboardMachine::Machine *> machines_;
+
+		class MultiKeyboard: public Inputs::Keyboard {
+			public:
+				MultiKeyboard(const std::vector<::KeyboardMachine::Machine *> &machines);
+
+				void set_key_pressed(Key key, char value, bool is_pressed) override;
+				void reset_all_keys() override;
+				const std::set<Key> &observed_keys() override;
+				bool is_exclusive() override;
+
+			private:
+				const std::vector<::KeyboardMachine::Machine *> &machines_;
+				std::set<Key> observed_keys_;
+				bool is_exclusive_ = false;
+		};
+		MultiKeyboard keyboard_;
+
 	public:
 		MultiKeyboardMachine(const std::vector<std::unique_ptr<::Machine::DynamicMachine>> &machines);
 
@@ -32,10 +51,7 @@ class MultiKeyboardMachine: public KeyboardMachine::Machine {
 		void clear_all_keys() override;
 		void set_key_state(uint16_t key, bool is_pressed) override;
 		void type_string(const std::string &) override;
-		void keyboard_did_change_key(Inputs::Keyboard *keyboard, Inputs::Keyboard::Key key, bool is_pressed) override;
-
-	private:
-		std::vector<::KeyboardMachine::Machine *> machines_;
+		Inputs::Keyboard &get_keyboard() override;
 };
 
 }

Analyser/Dynamic/MultiMachine/MultiMachine.cpp

@@ -7,6 +7,7 @@
 //
 
 #include "MultiMachine.hpp"
+#include "../../../Outputs/Log.hpp"
 
 #include <algorithm>
 
@@ -58,6 +59,11 @@ KeyboardMachine::Machine *MultiMachine::keyboard_machine() {
 	}
 }
 
+MouseMachine::Machine *MultiMachine::mouse_machine() {
+	// TODO.
+	return nullptr;
+}
+
 Configurable::Device *MultiMachine::configurable_device() {
 	if(has_picked_) {
 		return machines_.front()->configurable_device();
@@ -73,15 +79,13 @@ bool MultiMachine::would_collapse(const std::vector<std::unique_ptr<DynamicMachi
 }
 
 void MultiMachine::multi_crt_did_run_machines() {
-	std::lock_guard<std::mutex> machines_lock(machines_mutex_);
-#ifdef DEBUG
+	std::lock_guard<decltype(machines_mutex_)> machines_lock(machines_mutex_);
+#ifndef NDEBUG
 	for(const auto &machine: machines_) {
 		CRTMachine::Machine *crt = machine->crt_machine();
-		printf("%0.2f ", crt->get_confidence());
-		crt->print_type();
-		printf("; ");
+		LOGNBR(PADHEX(2) << crt->get_confidence() << " " << crt->debug_type() << "; ");
 	}
-	printf("\n");
+	LOGNBR(std::endl);
 #endif
 
 	DynamicMachine *front = machines_.front().get();

Analyser/Dynamic/MultiMachine/MultiMachine.hpp

@@ -54,6 +54,7 @@ class MultiMachine: public ::Machine::DynamicMachine, public MultiCRTMachine::De
 		Configurable::Device *configurable_device() override;
 		CRTMachine::Machine *crt_machine() override;
 		JoystickMachine::Machine *joystick_machine() override;
+		MouseMachine::Machine *mouse_machine() override;
 		KeyboardMachine::Machine *keyboard_machine() override;
 		MediaTarget::Machine *media_target() override;
 		void *raw_pointer() override;
@@ -62,7 +63,7 @@ class MultiMachine: public ::Machine::DynamicMachine, public MultiCRTMachine::De
 		void multi_crt_did_run_machines() override;
 
 		std::vector<std::unique_ptr<DynamicMachine>> machines_;
-		std::mutex machines_mutex_;
+		std::recursive_mutex machines_mutex_;
 
 		MultiConfigurable configurable_;
 		MultiCRTMachine crt_machine_;

Analyser/Machines.hpp

@@ -15,8 +15,11 @@ enum class Machine {
 	AmstradCPC,
 	AppleII,
 	Atari2600,
+	AtariST,
 	ColecoVision,
 	Electron,
+	Macintosh,
+	MasterSystem,
 	MSX,
 	Oric,
 	Vic20,

Analyser/Static/Acorn/Disk.cpp

@@ -18,7 +18,7 @@ using namespace Analyser::Static::Acorn;
 
 std::unique_ptr<Catalogue> Analyser::Static::Acorn::GetDFSCatalogue(const std::shared_ptr<Storage::Disk::Disk> &disk) {
 	// c.f. http://beebwiki.mdfs.net/Acorn_DFS_disc_format
-	std::unique_ptr<Catalogue> catalogue(new Catalogue);
+	auto catalogue = std::make_unique<Catalogue>();
 	Storage::Encodings::MFM::Parser parser(false, disk);
 
 	Storage::Encodings::MFM::Sector *names = parser.get_sector(0, 0, 0);
@@ -75,7 +75,7 @@ std::unique_ptr<Catalogue> Analyser::Static::Acorn::GetDFSCatalogue(const std::s
 	return catalogue;
 }
 std::unique_ptr<Catalogue> Analyser::Static::Acorn::GetADFSCatalogue(const std::shared_ptr<Storage::Disk::Disk> &disk) {
-	std::unique_ptr<Catalogue> catalogue(new Catalogue);
+	auto catalogue = std::make_unique<Catalogue>();
 	Storage::Encodings::MFM::Parser parser(true, disk);
 
 	Storage::Encodings::MFM::Sector *free_space_map_second_half = parser.get_sector(0, 0, 1);

Analyser/Static/Acorn/StaticAnalyser.cpp

@@ -58,7 +58,7 @@ static std::vector<std::shared_ptr<Storage::Cartridge::Cartridge>>
 }
 
 Analyser::Static::TargetList Analyser::Static::Acorn::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
-	std::unique_ptr<Target> target(new Target);
+	auto target = std::make_unique<Target>();
 	target->machine = Machine::Electron;
 	target->confidence = 0.5; // TODO: a proper estimation
 	target->has_dfs = false;

Analyser/Static/Acorn/Tape.cpp

@@ -16,7 +16,7 @@
 using namespace Analyser::Static::Acorn;
 
 static std::unique_ptr<File::Chunk> GetNextChunk(const std::shared_ptr<Storage::Tape::Tape> &tape, Storage::Tape::Acorn::Parser &parser) {
-	std::unique_ptr<File::Chunk> new_chunk(new File::Chunk);
+	auto new_chunk = std::make_unique<File::Chunk>();
 	int shift_register = 0;
 
 // TODO: move this into the parser
@@ -90,7 +90,7 @@ static std::unique_ptr<File> GetNextFile(std::deque<File::Chunk> &chunks) {
 	if(!chunks.size()) return nullptr;
 
 	// accumulate chunks for as long as block number is sequential and the end-of-file bit isn't set
-	std::unique_ptr<File> file(new File);
+	auto file = std::make_unique<File>();
 
 	uint16_t block_number = 0;
 

Analyser/Static/AmstradCPC/StaticAnalyser.cpp

@@ -181,7 +181,7 @@ static bool CheckBootSector(const std::shared_ptr<Storage::Disk::Disk> &disk, co
 
 Analyser::Static::TargetList Analyser::Static::AmstradCPC::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
 	TargetList destination;
-	std::unique_ptr<Target> target(new Target);
+	auto target = std::make_unique<Target>();
 	target->machine = Machine::AmstradCPC;
 	target->confidence = 0.5;
 

Analyser/Static/AppleII/StaticAnalyser.cpp

@@ -10,7 +10,7 @@
 #include "Target.hpp"
 
 Analyser::Static::TargetList Analyser::Static::AppleII::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
-	auto target = std::unique_ptr<Target>(new Target);
+	auto target = std::make_unique<Target>();
 	target->machine = Machine::AppleII;
 	target->media = media;
 

Analyser/Static/AppleII/Target.hpp

@@ -19,7 +19,8 @@ struct Target: public ::Analyser::Static::Target {
 	enum class Model {
 		II,
 		IIplus,
-		IIe
+		IIe,
+		EnhancedIIe
 	};
 	enum class DiskController {
 		None,

Analyser/Static/Atari2600/StaticAnalyser.cpp

@@ -12,9 +12,10 @@
 
 #include "../Disassembler/6502.hpp"
 
-using namespace Analyser::Static::Atari;
+using namespace Analyser::Static::Atari2600;
+using Target = Analyser::Static::Atari2600::Target;
 
-static void DeterminePagingFor2kCartridge(Analyser::Static::Atari::Target &target, const Storage::Cartridge::Cartridge::Segment &segment) {
+static void DeterminePagingFor2kCartridge(Target &target, const Storage::Cartridge::Cartridge::Segment &segment) {
 	// if this is a 2kb cartridge then it's definitely either unpaged or a CommaVid
 	uint16_t entry_address, break_address;
 
@@ -48,10 +49,10 @@ static void DeterminePagingFor2kCartridge(Analyser::Static::Atari::Target &targe
 	// caveat: false positives aren't likely to be problematic; a false positive is a 2KB ROM that always addresses
 	// itself so as to land in ROM even if mapped as a CommaVid and this code is on the fence as to whether it
 	// attempts to modify itself but it probably doesn't
-	if(has_wide_area_store) target.paging_model = Analyser::Static::Atari::Target::PagingModel::CommaVid;
+	if(has_wide_area_store) target.paging_model = Target::PagingModel::CommaVid;
 }
 
-static void DeterminePagingFor8kCartridge(Analyser::Static::Atari::Target &target, const Storage::Cartridge::Cartridge::Segment &segment, const Analyser::Static::MOS6502::Disassembly &disassembly) {
+static void DeterminePagingFor8kCartridge(Target &target, const Storage::Cartridge::Cartridge::Segment &segment, const Analyser::Static::MOS6502::Disassembly &disassembly) {
 	// Activision stack titles have their vectors at the top of the low 4k, not the top, and
 	// always list 0xf000 as both vectors; they do not repeat them, and, inexplicably, they all
 	// issue an SEI as their first instruction (maybe some sort of relic of the development environment?)
@@ -60,12 +61,12 @@ static void DeterminePagingFor8kCartridge(Analyser::Static::Atari::Target &targe
 		(segment.data[8191] != 0xf0 || segment.data[8189] != 0xf0 || segment.data[8190] != 0x00 || segment.data[8188] != 0x00) &&
 		segment.data[0] == 0x78
 	) {
-		target.paging_model = Analyser::Static::Atari::Target::PagingModel::ActivisionStack;
+		target.paging_model = Target::PagingModel::ActivisionStack;
 		return;
 	}
 
 	// make an assumption that this is the Atari paging model
-	target.paging_model = Analyser::Static::Atari::Target::PagingModel::Atari8k;
+	target.paging_model = Target::PagingModel::Atari8k;
 
 	std::set<uint16_t> internal_accesses;
 	internal_accesses.insert(disassembly.internal_stores.begin(), disassembly.internal_stores.end());
@@ -85,13 +86,13 @@ static void DeterminePagingFor8kCartridge(Analyser::Static::Atari::Target &targe
 		tigervision_access_count += masked_address == 0x3f;
 	}
 
-	if(parker_access_count > atari_access_count) target.paging_model = Analyser::Static::Atari::Target::PagingModel::ParkerBros;
-	else if(tigervision_access_count > atari_access_count) target.paging_model = Analyser::Static::Atari::Target::PagingModel::Tigervision;
+	if(parker_access_count > atari_access_count) target.paging_model = Target::PagingModel::ParkerBros;
+	else if(tigervision_access_count > atari_access_count) target.paging_model = Target::PagingModel::Tigervision;
 }
 
-static void DeterminePagingFor16kCartridge(Analyser::Static::Atari::Target &target, const Storage::Cartridge::Cartridge::Segment &segment, const Analyser::Static::MOS6502::Disassembly &disassembly) {
+static void DeterminePagingFor16kCartridge(Target &target, const Storage::Cartridge::Cartridge::Segment &segment, const Analyser::Static::MOS6502::Disassembly &disassembly) {
 	// make an assumption that this is the Atari paging model
-	target.paging_model = Analyser::Static::Atari::Target::PagingModel::Atari16k;
+	target.paging_model = Target::PagingModel::Atari16k;
 
 	std::set<uint16_t> internal_accesses;
 	internal_accesses.insert(disassembly.internal_stores.begin(), disassembly.internal_stores.end());
@@ -106,17 +107,17 @@ static void DeterminePagingFor16kCartridge(Analyser::Static::Atari::Target &targ
 		mnetwork_access_count += masked_address >= 0x1fe0 && masked_address < 0x1ffb;
 	}
 
-	if(mnetwork_access_count > atari_access_count) target.paging_model = Analyser::Static::Atari::Target::PagingModel::MNetwork;
+	if(mnetwork_access_count > atari_access_count) target.paging_model = Target::PagingModel::MNetwork;
 }
 
-static void DeterminePagingFor64kCartridge(Analyser::Static::Atari::Target &target, const Storage::Cartridge::Cartridge::Segment &segment, const Analyser::Static::MOS6502::Disassembly &disassembly) {
+static void DeterminePagingFor64kCartridge(Target &target, const Storage::Cartridge::Cartridge::Segment &segment, const Analyser::Static::MOS6502::Disassembly &disassembly) {
 	// make an assumption that this is a Tigervision if there is a write to 3F
 	target.paging_model =
 		(disassembly.external_stores.find(0x3f) != disassembly.external_stores.end()) ?
-			Analyser::Static::Atari::Target::PagingModel::Tigervision : Analyser::Static::Atari::Target::PagingModel::MegaBoy;
+			Target::PagingModel::Tigervision : Target::PagingModel::MegaBoy;
 }
 
-static void DeterminePagingForCartridge(Analyser::Static::Atari::Target &target, const Storage::Cartridge::Cartridge::Segment &segment) {
+static void DeterminePagingForCartridge(Target &target, const Storage::Cartridge::Cartridge::Segment &segment) {
 	if(segment.data.size() == 2048) {
 		DeterminePagingFor2kCartridge(target, segment);
 		return;
@@ -140,16 +141,16 @@ static void DeterminePagingForCartridge(Analyser::Static::Atari::Target &target,
 			DeterminePagingFor8kCartridge(target, segment, disassembly);
 		break;
 		case 10495:
-			target.paging_model = Analyser::Static::Atari::Target::PagingModel::Pitfall2;
+			target.paging_model = Target::PagingModel::Pitfall2;
 		break;
 		case 12288:
-			target.paging_model = Analyser::Static::Atari::Target::PagingModel::CBSRamPlus;
+			target.paging_model = Target::PagingModel::CBSRamPlus;
 		break;
 		case 16384:
 			DeterminePagingFor16kCartridge(target, segment, disassembly);
 		break;
 		case 32768:
-			target.paging_model = Analyser::Static::Atari::Target::PagingModel::Atari32k;
+			target.paging_model = Target::PagingModel::Atari32k;
 		break;
 		case 65536:
 			DeterminePagingFor64kCartridge(target, segment, disassembly);
@@ -161,8 +162,8 @@ static void DeterminePagingForCartridge(Analyser::Static::Atari::Target &target,
 	// check for a Super Chip. Atari ROM images [almost] always have the same value stored over RAM
 	// regions; when they don't they at least seem to have the first 128 bytes be the same as the
 	// next 128 bytes. So check for that.
-	if(	target.paging_model != Analyser::Static::Atari::Target::PagingModel::CBSRamPlus &&
-		target.paging_model != Analyser::Static::Atari::Target::PagingModel::MNetwork) {
+	if(	target.paging_model != Target::PagingModel::CBSRamPlus &&
+		target.paging_model != Target::PagingModel::MNetwork) {
 		bool has_superchip = true;
 		for(std::size_t address = 0; address < 128; address++) {
 			if(segment.data[address] != segment.data[address+128]) {
@@ -174,19 +175,19 @@ static void DeterminePagingForCartridge(Analyser::Static::Atari::Target &target,
 	}
 
 	// check for a Tigervision or Tigervision-esque scheme
-	if(target.paging_model == Analyser::Static::Atari::Target::PagingModel::None && segment.data.size() > 4096) {
+	if(target.paging_model == Target::PagingModel::None && segment.data.size() > 4096) {
 		bool looks_like_tigervision = disassembly.external_stores.find(0x3f) != disassembly.external_stores.end();
-		if(looks_like_tigervision) target.paging_model = Analyser::Static::Atari::Target::PagingModel::Tigervision;
+		if(looks_like_tigervision) target.paging_model = Target::PagingModel::Tigervision;
 	}
 }
 
-Analyser::Static::TargetList Analyser::Static::Atari::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
+Analyser::Static::TargetList Analyser::Static::Atari2600::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
 	// TODO: sanity checking; is this image really for an Atari 2600?
-	std::unique_ptr<Analyser::Static::Atari::Target> target(new Analyser::Static::Atari::Target);
+	auto target = std::make_unique<Target>();
 	target->machine = Machine::Atari2600;
 	target->confidence = 0.5;
 	target->media.cartridges = media.cartridges;
-	target->paging_model = Analyser::Static::Atari::Target::PagingModel::None;
+	target->paging_model = Target::PagingModel::None;
 	target->uses_superchip = false;
 
 	// try to figure out the paging scheme

Analyser/Static/Atari2600/StaticAnalyser.hpp

@@ -15,7 +15,7 @@
 
 namespace Analyser {
 namespace Static {
-namespace Atari {
+namespace Atari2600 {
 
 TargetList GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms);
 

Analyser/Static/Atari2600/Target.hpp

@@ -6,14 +6,14 @@
 //  Copyright 2018 Thomas Harte. All rights reserved.
 //
 
-#ifndef Analyser_Static_Atari_Target_h
-#define Analyser_Static_Atari_Target_h
+#ifndef Analyser_Static_Atari2600_Target_h
+#define Analyser_Static_Atari2600_Target_h
 
 #include "../StaticAnalyser.hpp"
 
 namespace Analyser {
 namespace Static {
-namespace Atari {
+namespace Atari2600 {
 
 struct Target: public ::Analyser::Static::Target {
 	enum class PagingModel {

Analyser/Static/AtariST/StaticAnalyser.cpp

@@ -0,0 +1,26 @@
+//
+//  StaticAnalyser.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 03/10/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "StaticAnalyser.hpp"
+#include "Target.hpp"
+
+Analyser::Static::TargetList Analyser::Static::AtariST::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
+	// This analyser can comprehend disks and mass-storage devices only.
+	if(media.disks.empty()) return {};
+
+	// As there is at least one usable media image, wave it through.
+	Analyser::Static::TargetList targets;
+
+	using Target = Analyser::Static::Target;
+	auto *target = new Target;
+	target->machine = Analyser::Machine::AtariST;
+	target->media = media;
+	targets.push_back(std::unique_ptr<Analyser::Static::Target>(target));
+
+	return targets;
+}

Analyser/Static/AtariST/StaticAnalyser.hpp

@@ -0,0 +1,27 @@
+//
+//  StaticAnalyser.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 03/10/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef Analyser_Static_AtariST_StaticAnalyser_hpp
+#define Analyser_Static_AtariST_StaticAnalyser_hpp
+
+#include "../StaticAnalyser.hpp"
+#include "../../../Storage/TargetPlatforms.hpp"
+#include <string>
+
+namespace Analyser {
+namespace Static {
+namespace AtariST {
+
+TargetList GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms);
+
+}
+}
+}
+
+
+#endif /* Analyser_Static_AtariST_StaticAnalyser_hpp */

Analyser/Static/AtariST/Target.hpp

@@ -0,0 +1,23 @@
+//
+//  Target.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 03/06/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef Analyser_Static_AtariST_Target_h
+#define Analyser_Static_AtariST_Target_h
+
+namespace Analyser {
+namespace Static {
+namespace AtariST {
+
+struct Target: public ::Analyser::Static::Target {
+};
+
+}
+}
+}
+
+#endif /* Analyser_Static_AtariST_Target_h */

Analyser/Static/Coleco/StaticAnalyser.cpp

@@ -54,7 +54,7 @@ static std::vector<std::shared_ptr<Storage::Cartridge::Cartridge>>
 
 Analyser::Static::TargetList Analyser::Static::Coleco::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
 	TargetList targets;
-	std::unique_ptr<Target> target(new Target);
+	auto target = std::make_unique<Target>();
 	target->machine = Machine::ColecoVision;
 	target->confidence = 1.0f - 1.0f / 32768.0f;
 	target->media.cartridges = ColecoCartridgesFrom(media.cartridges);

Analyser/Static/Coleco/StaticAnalyser.hpp

@@ -23,5 +23,4 @@ TargetList GetTargets(const Media &media, const std::string &file_name, TargetPl
 }
 }
 
-
 #endif /* StaticAnalyser_hpp */

Analyser/Static/Commodore/Disk.cpp

@@ -22,7 +22,7 @@ class CommodoreGCRParser: public Storage::Disk::Controller {
 		std::shared_ptr<Storage::Disk::Drive> drive;
 
 		CommodoreGCRParser() : Storage::Disk::Controller(4000000), shift_register_(0), track_(1) {
-			drive.reset(new Storage::Disk::Drive(4000000, 300, 2));
+			drive = std::make_shared<Storage::Disk::Drive>(4000000, 300, 2);
 			set_drive(drive);
 			drive->set_motor_on(true);
 		}
@@ -125,7 +125,7 @@ class CommodoreGCRParser: public Storage::Disk::Controller {
 		}
 
 		std::shared_ptr<Sector> get_next_sector() {
-			std::shared_ptr<Sector> sector(new Sector);
+			auto sector = std::make_shared<Sector>();
 			const int max_index_count = index_count_ + 2;
 
 			while(index_count_ < max_index_count) {

Analyser/Static/Commodore/StaticAnalyser.cpp

@@ -13,8 +13,10 @@
 #include "Tape.hpp"
 #include "Target.hpp"
 #include "../../../Storage/Cartridge/Encodings/CommodoreROM.hpp"
+#include "../../../Outputs/Log.hpp"
 
 #include <algorithm>
+#include <cstring>
 #include <sstream>
 
 using namespace Analyser::Static::Commodore;
@@ -43,7 +45,7 @@ static std::vector<std::shared_ptr<Storage::Cartridge::Cartridge>>
 Analyser::Static::TargetList Analyser::Static::Commodore::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
 	TargetList destination;
 
-	std::unique_ptr<Target> target(new Target);
+	auto target = std::make_unique<Target>();
 	target->machine = Machine::Vic20;	// TODO: machine estimation
 	target->confidence = 0.5; // TODO: a proper estimation
 
@@ -77,10 +79,10 @@ Analyser::Static::TargetList Analyser::Static::Commodore::GetTargets(const Media
 	}
 
 	if(!files.empty()) {
-		target->memory_model = Target::MemoryModel::Unexpanded;
+		auto memory_model = Target::MemoryModel::Unexpanded;
 		std::ostringstream string_stream;
 		string_stream << "LOAD\"" << (is_disk ? "*" : "") << "\"," << device << ",";
-  		if(files.front().is_basic()) {
+		if(files.front().is_basic()) {
 			string_stream << "0";
 		} else {
 			string_stream << "1";
@@ -91,18 +93,20 @@ Analyser::Static::TargetList Analyser::Static::Commodore::GetTargets(const Media
 		// make a first guess based on loading address
 		switch(files.front().starting_address) {
 			default:
-				printf("Starting address %04x?\n", files.front().starting_address);
+				LOG("Unrecognised loading address for Commodore program: " << PADHEX(4) <<  files.front().starting_address);
 			case 0x1001:
-				target->memory_model = Target::MemoryModel::Unexpanded;
+				memory_model = Target::MemoryModel::Unexpanded;
 			break;
 			case 0x1201:
-				target->memory_model = Target::MemoryModel::ThirtyTwoKB;
+				memory_model = Target::MemoryModel::ThirtyTwoKB;
 			break;
 			case 0x0401:
-				target->memory_model = Target::MemoryModel::EightKB;
+				memory_model = Target::MemoryModel::EightKB;
 			break;
 		}
 
+		target->set_memory_model(memory_model);
+
 		// General approach: increase memory size conservatively such that the largest file found will fit.
 //		for(File &file : files) {
 //			std::size_t file_size = file.data.size();
@@ -144,13 +148,52 @@ Analyser::Static::TargetList Analyser::Static::Commodore::GetTargets(const Media
 	}
 
 	if(!target->media.empty()) {
-		// Inspect filename for a region hint.
+		// Inspect filename for configuration hints.
 		std::string lowercase_name = file_name;
 		std::transform(lowercase_name.begin(), lowercase_name.end(), lowercase_name.begin(), ::tolower);
+
+		// Hint 1: 'ntsc' anywhere in the name implies America.
 		if(lowercase_name.find("ntsc") != std::string::npos) {
 			target->region = Analyser::Static::Commodore::Target::Region::American;
 		}
 
+		// Potential additional hints: check for TheC64 tags.
+		auto final_underscore = lowercase_name.find_last_of('_');
+		if(final_underscore != std::string::npos) {
+			auto iterator = lowercase_name.begin() + ssize_t(final_underscore) + 1;
+
+			while(iterator != lowercase_name.end()) {
+				// Grab the next tag.
+				char next_tag[3] = {0, 0, 0};
+				next_tag[0] = *iterator++;
+				if(iterator == lowercase_name.end()) break;
+				next_tag[1] = *iterator++;
+
+				// Exit early if attempting to read another tag has run over the file extension.
+				if(next_tag[0] == '.' || next_tag[1] == '.') break;
+
+				// Check whether it's anything.
+				target->enabled_ram.bank0 |= !strcmp(next_tag, "b0");
+				target->enabled_ram.bank1 |= !strcmp(next_tag, "b1");
+				target->enabled_ram.bank2 |= !strcmp(next_tag, "b2");
+				target->enabled_ram.bank3 |= !strcmp(next_tag, "b3");
+				target->enabled_ram.bank5 |= !strcmp(next_tag, "b5");
+				if(!strcmp(next_tag, "tn")) {	// i.e. NTSC.
+					target->region = Analyser::Static::Commodore::Target::Region::American;
+				}
+				if(!strcmp(next_tag, "tp")) {	// i.e. PAL.
+					target->region = Analyser::Static::Commodore::Target::Region::European;
+				}
+
+				// Unhandled:
+				//
+				//	M6: 	this is a C64 file.
+				//	MV: 	this is a Vic-20 file.
+				//	J1/J2:	this C64 file should have the primary joystick in slot 1/2.
+				//	RO:		this disk image should be treated as read-only.
+			}
+		}
+
 		// Attach a 1540 if there are any disks here.
 		target->has_c1540 = !target->media.disks.empty();
 

Analyser/Static/Commodore/Target.hpp

@@ -31,7 +31,26 @@ struct Target: public ::Analyser::Static::Target {
 		Swedish
 	};
 
-	MemoryModel memory_model = MemoryModel::Unexpanded;
+	/// Maps from a named memory model to a bank enabled/disabled set.
+	void set_memory_model(MemoryModel memory_model) {
+		// This is correct for unexpanded and 32kb memory models.
+		enabled_ram.bank0 = enabled_ram.bank1 =
+		enabled_ram.bank2 = enabled_ram.bank3 =
+		enabled_ram.bank5 = memory_model == MemoryModel::ThirtyTwoKB;
+
+		// Bank 0 will need to be enabled if this is an 8kb machine.
+		enabled_ram.bank0 |= memory_model == MemoryModel::EightKB;
+	}
+	struct {
+		bool bank0 = false;
+		bool bank1 = false;
+		bool bank2 = false;
+		bool bank3 = false;
+		bool bank5 = false;
+					// Sic. There is no bank 4; this is because the area that logically would be
+					// bank 4 is occupied by the character ROM, colour RAM, hardware registers, etc.
+	} enabled_ram;
+
 	Region region = Region::European;
 	bool has_c1540 = false;
 	std::string loading_command;

Analyser/Static/Disassembler/Z80.cpp

@@ -63,9 +63,9 @@ class Accessor {
 #define z(v) (v & 7)
 
 Instruction::Condition condition_table[] = {
-	Instruction::Condition::NZ, 	Instruction::Condition::Z,
-	Instruction::Condition::NC, 	Instruction::Condition::C,
-	Instruction::Condition::PO, 	Instruction::Condition::PE,
+	Instruction::Condition::NZ,		Instruction::Condition::Z,
+	Instruction::Condition::NC,		Instruction::Condition::C,
+	Instruction::Condition::PO,		Instruction::Condition::PE,
 	Instruction::Condition::P,		Instruction::Condition::M
 };
 

Analyser/Static/MSX/StaticAnalyser.cpp

@@ -34,7 +34,7 @@ static std::unique_ptr<Analyser::Static::Target> CartridgeTarget(
 		output_segments.emplace_back(start_address, segment.data);
 	}
 
-	std::unique_ptr<Analyser::Static::MSX::Target> target(new Analyser::Static::MSX::Target);
+	auto target = std::make_unique<Analyser::Static::MSX::Target>();
 	target->machine = Analyser::Machine::MSX;
 	target->confidence = confidence;
 
@@ -269,7 +269,7 @@ Analyser::Static::TargetList Analyser::Static::MSX::GetTargets(const Media &medi
 	std::move(cartridge_targets.begin(), cartridge_targets.end(), std::back_inserter(destination));
 
 	// Consider building a target for disks and/or tapes.
-	std::unique_ptr<Target> target(new Target);
+	auto target = std::make_unique<Target>();
 
 	// Check tapes for loadable files.
 	for(auto &tape : media.tapes) {
@@ -285,7 +285,12 @@ Analyser::Static::TargetList Analyser::Static::MSX::GetTargets(const Media &medi
 		}
 	}
 
+	// Region selection: for now, this as simple as:
+	// "If a tape is involved, be European. Otherwise be American (i.e. English, but 60Hz)".
+	target->region = target->media.tapes.empty() ? Target::Region::USA : Target::Region::Europe;
+
 	// Blindly accept disks for now.
+	// TODO: how to spot an MSX disk?
 	target->media.disks = media.disks;
 	target->has_disk_drive = !media.disks.empty();
 

Analyser/Static/MSX/Target.hpp

@@ -19,6 +19,12 @@ namespace MSX {
 struct Target: public ::Analyser::Static::Target {
 	bool has_disk_drive = false;
 	std::string loading_command;
+
+	enum class Region {
+		Japan,
+		USA,
+		Europe
+	} region = Region::USA;
 };
 
 }

Analyser/Static/Macintosh/StaticAnalyser.cpp

@@ -0,0 +1,26 @@
+//
+//  StaticAnalyser.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 02/06/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "StaticAnalyser.hpp"
+#include "Target.hpp"
+
+Analyser::Static::TargetList Analyser::Static::Macintosh::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
+	// This analyser can comprehend disks and mass-storage devices only.
+	if(media.disks.empty() && media.mass_storage_devices.empty()) return {};
+
+	// As there is at least one usable media image, wave it through.
+	Analyser::Static::TargetList targets;
+
+	using Target = Analyser::Static::Macintosh::Target;
+	auto *target = new Target;
+	target->machine = Analyser::Machine::Macintosh;
+	target->media = media;
+	targets.push_back(std::unique_ptr<Analyser::Static::Target>(target));
+
+	return targets;
+}

Analyser/Static/Macintosh/StaticAnalyser.hpp

@@ -0,0 +1,27 @@
+//
+//  StaticAnalyser.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 02/06/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef Analyser_Static_Macintosh_StaticAnalyser_hpp
+#define Analyser_Static_Macintosh_StaticAnalyser_hpp
+
+#include "../StaticAnalyser.hpp"
+#include "../../../Storage/TargetPlatforms.hpp"
+#include <string>
+
+namespace Analyser {
+namespace Static {
+namespace Macintosh {
+
+TargetList GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms);
+
+}
+}
+}
+
+
+#endif /* Analyser_Static_Macintosh_StaticAnalyser_hpp */

Analyser/Static/Macintosh/Target.hpp

@@ -0,0 +1,31 @@
+//
+//  Target.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 03/06/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef Analyser_Static_Macintosh_Target_h
+#define Analyser_Static_Macintosh_Target_h
+
+namespace Analyser {
+namespace Static {
+namespace Macintosh {
+
+struct Target: public ::Analyser::Static::Target {
+	enum class Model {
+		Mac128k,
+		Mac512k,
+		Mac512ke,
+		MacPlus
+	};
+
+	Model model = Model::MacPlus;
+};
+
+}
+}
+}
+
+#endif /* Analyser_Static_Macintosh_Target_h */

Analyser/Static/Oric/StaticAnalyser.cpp

@@ -20,7 +20,9 @@
 
 using namespace Analyser::Static::Oric;
 
-static int Score(const Analyser::Static::MOS6502::Disassembly &disassembly, const std::set<uint16_t> &rom_functions, const std::set<uint16_t> &variable_locations) {
+namespace {
+
+int score(const Analyser::Static::MOS6502::Disassembly &disassembly, const std::set<uint16_t> &rom_functions, const std::set<uint16_t> &variable_locations) {
 	int score = 0;
 
 	for(const auto address : disassembly.outward_calls)		score += (rom_functions.find(address) != rom_functions.end()) ? 1 : -1;
@@ -30,7 +32,7 @@ static int Score(const Analyser::Static::MOS6502::Disassembly &disassembly, cons
 	return score;
 }
 
-static int Basic10Score(const Analyser::Static::MOS6502::Disassembly &disassembly) {
+int basic10_score(const Analyser::Static::MOS6502::Disassembly &disassembly) {
 	const std::set<uint16_t> rom_functions = {
 		0x0228,	0x022b,
 		0xc3ca,	0xc3f8,	0xc448,	0xc47c,	0xc4b5,	0xc4e3,	0xc4e0,	0xc524,	0xc56f,	0xc5a2,	0xc5f8,	0xc60a,	0xc6a5,	0xc6de,	0xc719,	0xc738,
@@ -51,10 +53,10 @@ static int Basic10Score(const Analyser::Static::MOS6502::Disassembly &disassembl
 		0x0228, 0x0229, 0x022a, 0x022b, 0x022c, 0x022d, 0x0230
 	};
 
-	return Score(disassembly, rom_functions, variable_locations);
+	return score(disassembly, rom_functions, variable_locations);
 }
 
-static int Basic11Score(const Analyser::Static::MOS6502::Disassembly &disassembly) {
+int basic11_score(const Analyser::Static::MOS6502::Disassembly &disassembly) {
 	const std::set<uint16_t> rom_functions = {
 		0x0238,	0x023b,	0x023e,	0x0241,	0x0244,	0x0247,
 		0xc3c6,	0xc3f4,	0xc444,	0xc47c,	0xc4a8,	0xc4d3,	0xc4e0,	0xc524,	0xc55f,	0xc592,	0xc5e8,	0xc5fa,	0xc692,	0xc6b3,	0xc6ee,	0xc70d,
@@ -76,10 +78,10 @@ static int Basic11Score(const Analyser::Static::MOS6502::Disassembly &disassembl
 		0x0244, 0x0245, 0x0246, 0x0247, 0x0248, 0x0249, 0x024a, 0x024b, 0x024c
 	};
 
-	return Score(disassembly, rom_functions, variable_locations);
+	return score(disassembly, rom_functions, variable_locations);
 }
 
-static bool IsMicrodisc(Storage::Encodings::MFM::Parser &parser) {
+bool is_microdisc(Storage::Encodings::MFM::Parser &parser) {
 	/*
 		The Microdisc boot sector is sector 2 of track 0 and contains a 23-byte signature.
 	*/
@@ -100,8 +102,51 @@ static bool IsMicrodisc(Storage::Encodings::MFM::Parser &parser) {
 	return !std::memcmp(signature, first_sample.data(), sizeof(signature));
 }
 
+bool is_400_loader(Storage::Encodings::MFM::Parser &parser, uint16_t range_start, uint16_t range_end) {
+	/*
+		Both the Jasmin and BD-DOS boot sectors are sector 1 of track 0 and are loaded at $400;
+		use disassembly to test for likely matches.
+	*/
+
+	Storage::Encodings::MFM::Sector *sector = parser.get_sector(0, 0, 1);
+	if(!sector) return false;
+	if(sector->samples.empty()) return false;
+
+	// Take a copy of the first sampling, and keep only the final 256 bytes (assuming at least that many were found).
+	std::vector<uint8_t> first_sample = sector->samples[0];
+	if(first_sample.size() < 256) return false;
+	if(first_sample.size() > 256) {
+		first_sample.erase(first_sample.end() - 256, first_sample.end());
+	}
+
+	// Grab a disassembly.
+	const auto disassembly =
+		Analyser::Static::MOS6502::Disassemble(first_sample, Analyser::Static::Disassembler::OffsetMapper(0x400), {0x400});
+
+	// Check for references to the Jasmin registers.
+	int register_hits = 0;
+	for(auto list : {disassembly.external_stores, disassembly.external_loads, disassembly.external_modifies}) {
+		for(auto address : list) {
+			register_hits += (address >= range_start && address <= range_end);
+		}
+	}
+
+	// Arbitrary, sure, but as long as at least two accesses to the requested register range are found, accept this.
+	return register_hits >= 2;
+}
+
+bool is_jasmin(Storage::Encodings::MFM::Parser &parser) {
+	return is_400_loader(parser, 0x3f4, 0x3ff);
+}
+
+bool is_bd500(Storage::Encodings::MFM::Parser &parser) {
+	return is_400_loader(parser, 0x310, 0x323);
+}
+
+}
+
 Analyser::Static::TargetList Analyser::Static::Oric::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
-	std::unique_ptr<Target> target(new Target);
+	auto target = std::make_unique<Target>();
 	target->machine = Machine::Oric;
 	target->confidence = 0.5;
 
@@ -115,12 +160,10 @@ Analyser::Static::TargetList Analyser::Static::Oric::GetTargets(const Media &med
 			for(const auto &file : tape_files) {
 				if(file.data_type == File::MachineCode) {
 					std::vector<uint16_t> entry_points = {file.starting_address};
-					Analyser::Static::MOS6502::Disassembly disassembly =
+					const Analyser::Static::MOS6502::Disassembly disassembly =
 						Analyser::Static::MOS6502::Disassemble(file.data, Analyser::Static::Disassembler::OffsetMapper(file.starting_address), entry_points);
 
-					int basic10_score = Basic10Score(disassembly);
-					int basic11_score = Basic11Score(disassembly);
-					if(basic10_score > basic11_score) basic10_votes++; else basic11_votes++;
+					if(basic10_score(disassembly) > basic11_score(disassembly)) ++basic10_votes; else ++basic11_votes;
 				}
 			}
 
@@ -130,12 +173,22 @@ Analyser::Static::TargetList Analyser::Static::Oric::GetTargets(const Media &med
 	}
 
 	if(!media.disks.empty()) {
-		// Only the Microdisc is emulated right now, so accept only disks that it can boot from.
+		// 8-DOS is recognised by a dedicated Disk II analyser, so check only for Microdisc,
+		// Jasmin and BD-DOS formats here.
 		for(auto &disk: media.disks) {
 			Storage::Encodings::MFM::Parser parser(true, disk);
-			if(IsMicrodisc(parser)) {
+
+			if(is_microdisc(parser)) {
 				target->disk_interface = Target::DiskInterface::Microdisc;
 				target->media.disks.push_back(disk);
+			} else if(is_jasmin(parser)) {
+				target->disk_interface = Target::DiskInterface::Jasmin;
+				target->should_start_jasmin = true;
+				target->media.disks.push_back(disk);
+			} else if(is_bd500(parser)) {
+				target->disk_interface = Target::DiskInterface::BD500;
+				target->media.disks.push_back(disk);
+				target->rom = Target::ROM::BASIC10;
 			}
 		}
 	}

Analyser/Static/Oric/Target.hpp

@@ -26,12 +26,15 @@ struct Target: public ::Analyser::Static::Target {
 	enum class DiskInterface {
 		Microdisc,
 		Pravetz,
+		Jasmin,
+		BD500,
 		None
 	};
 
 	ROM rom = ROM::BASIC11;
 	DiskInterface disk_interface = DiskInterface::None;
 	std::string loading_command;
+	bool should_start_jasmin = false;
 };
 
 }

Analyser/Static/Sega/StaticAnalyser.cpp

@@ -0,0 +1,82 @@
+//
+//  StaticAnalyser.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 20/09/2018.
+//  Copyright © 2018 Thomas Harte. All rights reserved.
+//
+
+#include "StaticAnalyser.hpp"
+
+#include "Target.hpp"
+
+#include <algorithm>
+#include <cstring>
+
+Analyser::Static::TargetList Analyser::Static::Sega::GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms) {
+	if(media.cartridges.empty())
+		return {};
+
+	TargetList targets;
+	auto target = std::make_unique<Target>();
+
+	target->machine = Machine::MasterSystem;
+
+	// Files named .sg are treated as for the SG1000; otherwise assume a Master System.
+	if(file_name.size() >= 2 && *(file_name.end() - 2) == 's' && *(file_name.end() - 1) == 'g') {
+		target->model = Target::Model::SG1000;
+	} else {
+		target->model = Target::Model::MasterSystem;
+	}
+
+	// If this is a Master System title, look for a ROM header.
+	if(target->model == Target::Model::MasterSystem) {
+		const auto &data = media.cartridges.front()->get_segments()[0].data;
+
+		// First try to locate a header.
+		size_t header_offset = 0;
+		size_t potential_offsets[] = {0x1ff0, 0x3ff0, 0x7ff0};
+		for(auto potential_offset: potential_offsets) {
+			if(!memcmp(&data[potential_offset], "TMR SEGA", 8)) {
+				header_offset = potential_offset;
+				break;
+			}
+		}
+
+		// If a header was found, use it to crib region.
+		if(header_offset) {
+			// Treat export titles as European by default; decline to
+			// do so only if (US) or (NTSC) is in the file name.
+			const uint8_t region = data[header_offset + 0x0f] >> 4;
+			switch(region) {
+				default: break;
+				case 4: {
+					std::string lowercase_name = file_name;
+					std::transform(lowercase_name.begin(), lowercase_name.end(), lowercase_name.begin(), ::tolower);
+					if(lowercase_name.find("(jp)") == std::string::npos) {
+						target->region =
+							(lowercase_name.find("(us)") == std::string::npos &&
+							lowercase_name.find("(ntsc)") == std::string::npos) ? Target::Region::Europe : Target::Region::USA;
+					}
+				} break;
+			}
+
+			// Also check for a Codemasters header.
+			// If one is found, set the paging scheme appropriately.
+			const uint16_t inverse_checksum = uint16_t(0x10000 - (data[0x7fe6] | (data[0x7fe7] << 8)));
+			if(
+				data[0x7fe3] >= 0x87 && data[0x7fe3] < 0x96 &&									// i.e. game is dated between 1987 and 1996
+				(inverse_checksum&0xff) == data[0x7fe8] &&
+				(inverse_checksum >> 8) == data[0x7fe9] &&										// i.e. the standard checksum appears to be present
+				!data[0x7fea] && !data[0x7feb] && !data[0x7fec] && !data[0x7fed] && !data[0x7fee] && !data[0x7fef]
+			) {
+				target->paging_scheme = Target::PagingScheme::Codemasters;
+				target->model = Target::Model::MasterSystem2;
+			}
+		}
+	}
+
+	target->media.cartridges = media.cartridges;
+	targets.push_back(std::move(target));
+	return targets;
+}

Analyser/Static/Sega/StaticAnalyser.hpp

@@ -0,0 +1,26 @@
+//
+//  StaticAnalyser.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 20/09/2018.
+//  Copyright © 2018 Thomas Harte. All rights reserved.
+//
+
+#ifndef StaticAnalyser_Sega_StaticAnalyser_hpp
+#define StaticAnalyser_Sega_StaticAnalyser_hpp
+
+#include "../StaticAnalyser.hpp"
+#include "../../../Storage/TargetPlatforms.hpp"
+#include <string>
+
+namespace Analyser {
+namespace Static {
+namespace Sega {
+
+TargetList GetTargets(const Media &media, const std::string &file_name, TargetPlatform::IntType potential_platforms);
+
+}
+}
+}
+
+#endif /* StaticAnalyser_hpp */

Analyser/Static/Sega/Target.hpp

@@ -0,0 +1,46 @@
+//
+//  Target.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 23/09/2018.
+//  Copyright © 2018 Thomas Harte. All rights reserved.
+//
+
+#ifndef Analyser_Static_Sega_Target_h
+#define Analyser_Static_Sega_Target_h
+
+namespace Analyser {
+namespace Static {
+namespace Sega {
+
+struct Target: public ::Analyser::Static::Target {
+	enum class Model {
+		SG1000,
+		MasterSystem,
+		MasterSystem2,
+	};
+
+	enum class Region {
+		Japan,
+		USA,
+		Europe,
+		Brazil
+	};
+
+	enum class PagingScheme {
+		Sega,
+		Codemasters
+	};
+
+	Model model = Model::MasterSystem;
+	Region region = Region::Japan;
+	PagingScheme paging_scheme = PagingScheme::Sega;
+};
+
+#define is_master_system(v) v >= Analyser::Static::Sega::Target::Model::MasterSystem
+
+}
+}
+}
+
+#endif /* Analyser_Static_Sega_Target_h */

Analyser/Static/StaticAnalyser.cpp

@@ -17,12 +17,15 @@
 #include "Acorn/StaticAnalyser.hpp"
 #include "AmstradCPC/StaticAnalyser.hpp"
 #include "AppleII/StaticAnalyser.hpp"
-#include "Atari/StaticAnalyser.hpp"
+#include "Atari2600/StaticAnalyser.hpp"
+#include "AtariST/StaticAnalyser.hpp"
 #include "Coleco/StaticAnalyser.hpp"
 #include "Commodore/StaticAnalyser.hpp"
 #include "DiskII/StaticAnalyser.hpp"
+#include "Macintosh/StaticAnalyser.hpp"
 #include "MSX/StaticAnalyser.hpp"
 #include "Oric/StaticAnalyser.hpp"
+#include "Sega/StaticAnalyser.hpp"
 #include "ZX8081/StaticAnalyser.hpp"
 
 // Cartridges
@@ -34,15 +37,22 @@
 #include "../../Storage/Disk/DiskImage/Formats/AppleDSK.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/CPCDSK.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/D64.hpp"
+#include "../../Storage/Disk/DiskImage/Formats/MacintoshIMG.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/G64.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/DMK.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/HFE.hpp"
+#include "../../Storage/Disk/DiskImage/Formats/MSA.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/MSXDSK.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/NIB.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/OricMFMDSK.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/SSD.hpp"
+#include "../../Storage/Disk/DiskImage/Formats/ST.hpp"
+#include "../../Storage/Disk/DiskImage/Formats/STX.hpp"
 #include "../../Storage/Disk/DiskImage/Formats/WOZ.hpp"
 
+// Mass Storage Devices (i.e. usually, hard disks)
+#include "../../Storage/MassStorage/Formats/HFV.hpp"
+
 // Tapes
 #include "../../Storage/Tape/Formats/CAS.hpp"
 #include "../../Storage/Tape/Formats/CommodoreTAP.hpp"
@@ -84,34 +94,39 @@ static Media GetMediaAndPlatforms(const std::string &file_name, TargetPlatform::
 		TryInsert(list, class, platforms)	\
 	}
 
-	Format("80", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)										// 80
-	Format("81", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)										// 81
-	Format("a26", result.cartridges, Cartridge::BinaryDump, TargetPlatform::Atari2600)						// A26
-	Format("adf", result.disks, Disk::DiskImageHolder<Storage::Disk::AcornADF>, TargetPlatform::Acorn)		// ADF
-	Format("bin", result.cartridges, Cartridge::BinaryDump, TargetPlatform::AllCartridge)					// BIN
-	Format("cas", result.tapes, Tape::CAS, TargetPlatform::MSX)												// CAS
-	Format("cdt", result.tapes, Tape::TZX, TargetPlatform::AmstradCPC)										// CDT
-	Format("col", result.cartridges, Cartridge::BinaryDump, TargetPlatform::ColecoVision)					// COL
-	Format("csw", result.tapes, Tape::CSW, TargetPlatform::AllTape)											// CSW
-	Format("d64", result.disks, Disk::DiskImageHolder<Storage::Disk::D64>, TargetPlatform::Commodore)		// D64
-	Format("dmk", result.disks, Disk::DiskImageHolder<Storage::Disk::DMK>, TargetPlatform::MSX)				// DMK
-	Format("do", result.disks, Disk::DiskImageHolder<Storage::Disk::AppleDSK>, TargetPlatform::DiskII)		// DO
-	Format("dsd", result.disks, Disk::DiskImageHolder<Storage::Disk::SSD>, TargetPlatform::Acorn)			// DSD
-	Format("dsk", result.disks, Disk::DiskImageHolder<Storage::Disk::CPCDSK>, TargetPlatform::AmstradCPC)	// DSK (Amstrad CPC)
-	Format("dsk", result.disks, Disk::DiskImageHolder<Storage::Disk::AppleDSK>, TargetPlatform::DiskII)		// DSK (Apple)
-	Format("dsk", result.disks, Disk::DiskImageHolder<Storage::Disk::MSXDSK>, TargetPlatform::MSX)			// DSK (MSX)
-	Format("dsk", result.disks, Disk::DiskImageHolder<Storage::Disk::OricMFMDSK>, TargetPlatform::Oric)		// DSK (Oric)
-	Format("g64", result.disks, Disk::DiskImageHolder<Storage::Disk::G64>, TargetPlatform::Commodore)		// G64
+	Format("80", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)											// 80
+	Format("81", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)											// 81
+	Format("a26", result.cartridges, Cartridge::BinaryDump, TargetPlatform::Atari2600)							// A26
+	Format("adf", result.disks, Disk::DiskImageHolder<Storage::Disk::AcornADF>, TargetPlatform::Acorn)			// ADF
+	Format("bin", result.cartridges, Cartridge::BinaryDump, TargetPlatform::AllCartridge)						// BIN (cartridge dump)
+	Format("cas", result.tapes, Tape::CAS, TargetPlatform::MSX)													// CAS
+	Format("cdt", result.tapes, Tape::TZX, TargetPlatform::AmstradCPC)											// CDT
+	Format("col", result.cartridges, Cartridge::BinaryDump, TargetPlatform::ColecoVision)						// COL
+	Format("csw", result.tapes, Tape::CSW, TargetPlatform::AllTape)												// CSW
+	Format("d64", result.disks, Disk::DiskImageHolder<Storage::Disk::D64>, TargetPlatform::Commodore)			// D64
+	Format("dmk", result.disks, Disk::DiskImageHolder<Storage::Disk::DMK>, TargetPlatform::MSX)					// DMK
+	Format("do", result.disks, Disk::DiskImageHolder<Storage::Disk::AppleDSK>, TargetPlatform::DiskII)			// DO
+	Format("dsd", result.disks, Disk::DiskImageHolder<Storage::Disk::SSD>, TargetPlatform::Acorn)				// DSD
+	Format("dsk", result.disks, Disk::DiskImageHolder<Storage::Disk::CPCDSK>, TargetPlatform::AmstradCPC)		// DSK (Amstrad CPC)
+	Format("dsk", result.disks, Disk::DiskImageHolder<Storage::Disk::AppleDSK>, TargetPlatform::DiskII)			// DSK (Apple II)
+	Format("dsk", result.disks, Disk::DiskImageHolder<Storage::Disk::MacintoshIMG>, TargetPlatform::Macintosh)	// DSK (Macintosh, floppy disk)
+	Format("dsk", result.mass_storage_devices, MassStorage::HFV, TargetPlatform::Macintosh)						// DSK (Macintosh, hard disk)
+	Format("dsk", result.disks, Disk::DiskImageHolder<Storage::Disk::MSXDSK>, TargetPlatform::MSX)				// DSK (MSX)
+	Format("dsk", result.disks, Disk::DiskImageHolder<Storage::Disk::OricMFMDSK>, TargetPlatform::Oric)			// DSK (Oric)
+	Format("g64", result.disks, Disk::DiskImageHolder<Storage::Disk::G64>, TargetPlatform::Commodore)			// G64
 	Format(	"hfe",
 			result.disks,
 			Disk::DiskImageHolder<Storage::Disk::HFE>,
 			TargetPlatform::Acorn | TargetPlatform::AmstradCPC | TargetPlatform::Commodore | TargetPlatform::Oric)
 			// HFE (TODO: switch to AllDisk once the MSX stops being so greedy)
-	Format("nib", result.disks, Disk::DiskImageHolder<Storage::Disk::NIB>, TargetPlatform::DiskII)			// NIB
-	Format("o", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)										// O
-	Format("p", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)										// P
-	Format("po", result.disks, Disk::DiskImageHolder<Storage::Disk::AppleDSK>, TargetPlatform::DiskII)		// PO
-	Format("p81", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)										// P81
+	Format("img", result.disks, Disk::DiskImageHolder<Storage::Disk::MacintoshIMG>, TargetPlatform::Macintosh)		// IMG (DiskCopy 4.2)
+	Format("image", result.disks, Disk::DiskImageHolder<Storage::Disk::MacintoshIMG>, TargetPlatform::Macintosh)	// IMG (DiskCopy 4.2)
+	Format("msa", result.disks, Disk::DiskImageHolder<Storage::Disk::MSA>, TargetPlatform::AtariST)				// MSA
+	Format("nib", result.disks, Disk::DiskImageHolder<Storage::Disk::NIB>, TargetPlatform::DiskII)				// NIB
+	Format("o", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)											// O
+	Format("p", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)											// P
+	Format("po", result.disks, Disk::DiskImageHolder<Storage::Disk::AppleDSK>, TargetPlatform::DiskII)			// PO
+	Format("p81", result.tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)											// P81
 
 	// PRG
 	if(extension == "prg") {
@@ -128,14 +143,18 @@ static Media GetMediaAndPlatforms(const std::string &file_name, TargetPlatform::
 	Format(	"rom",
 			result.cartridges,
 			Cartridge::BinaryDump,
-			TargetPlatform::AcornElectron | TargetPlatform::ColecoVision | TargetPlatform::MSX)				// ROM
-	Format("ssd", result.disks, Disk::DiskImageHolder<Storage::Disk::SSD>, TargetPlatform::Acorn)			// SSD
-	Format("tap", result.tapes, Tape::CommodoreTAP, TargetPlatform::Commodore)								// TAP (Commodore)
-	Format("tap", result.tapes, Tape::OricTAP, TargetPlatform::Oric)										// TAP (Oric)
-	Format("tsx", result.tapes, Tape::TZX, TargetPlatform::MSX)												// TSX
-	Format("tzx", result.tapes, Tape::TZX, TargetPlatform::ZX8081)											// TZX
-	Format("uef", result.tapes, Tape::UEF, TargetPlatform::Acorn)											// UEF (tape)
-	Format("woz", result.disks, Disk::DiskImageHolder<Storage::Disk::WOZ>, TargetPlatform::DiskII)			// WOZ
+			TargetPlatform::AcornElectron | TargetPlatform::ColecoVision | TargetPlatform::MSX)					// ROM
+	Format("sg", result.cartridges, Cartridge::BinaryDump, TargetPlatform::Sega)								// SG
+	Format("sms", result.cartridges, Cartridge::BinaryDump, TargetPlatform::Sega)								// SMS
+	Format("ssd", result.disks, Disk::DiskImageHolder<Storage::Disk::SSD>, TargetPlatform::Acorn)				// SSD
+	Format("st", result.disks, Disk::DiskImageHolder<Storage::Disk::ST>, TargetPlatform::AtariST)				// ST
+	Format("stx", result.disks, Disk::DiskImageHolder<Storage::Disk::STX>, TargetPlatform::AtariST)				// STX
+	Format("tap", result.tapes, Tape::CommodoreTAP, TargetPlatform::Commodore)									// TAP (Commodore)
+	Format("tap", result.tapes, Tape::OricTAP, TargetPlatform::Oric)											// TAP (Oric)
+	Format("tsx", result.tapes, Tape::TZX, TargetPlatform::MSX)													// TSX
+	Format("tzx", result.tapes, Tape::TZX, TargetPlatform::ZX8081)												// TZX
+	Format("uef", result.tapes, Tape::UEF, TargetPlatform::Acorn)												// UEF (tape)
+	Format("woz", result.disks, Disk::DiskImageHolder<Storage::Disk::WOZ>, TargetPlatform::DiskII)				// WOZ
 
 #undef Format
 #undef Insert
@@ -152,7 +171,7 @@ Media Analyser::Static::GetMedia(const std::string &file_name) {
 TargetList Analyser::Static::GetTargets(const std::string &file_name) {
 	TargetList targets;
 
-	// Collect all disks, tapes and ROMs as can be extrapolated from this file, forming the
+	// Collect all disks, tapes ROMs, etc as can be extrapolated from this file, forming the
 	// union of all platforms this file might be a target for.
 	TargetPlatform::IntType potential_platforms = 0;
 	Media media = GetMediaAndPlatforms(file_name, potential_platforms);
@@ -166,12 +185,15 @@ TargetList Analyser::Static::GetTargets(const std::string &file_name) {
 	if(potential_platforms & TargetPlatform::Acorn)			Append(Acorn);
 	if(potential_platforms & TargetPlatform::AmstradCPC)	Append(AmstradCPC);
 	if(potential_platforms & TargetPlatform::AppleII)		Append(AppleII);
-	if(potential_platforms & TargetPlatform::Atari2600)		Append(Atari);
+	if(potential_platforms & TargetPlatform::Atari2600)		Append(Atari2600);
+	if(potential_platforms & TargetPlatform::AtariST)		Append(AtariST);
 	if(potential_platforms & TargetPlatform::ColecoVision)	Append(Coleco);
 	if(potential_platforms & TargetPlatform::Commodore)		Append(Commodore);
 	if(potential_platforms & TargetPlatform::DiskII)		Append(DiskII);
+	if(potential_platforms & TargetPlatform::Macintosh)		Append(Macintosh);
 	if(potential_platforms & TargetPlatform::MSX)			Append(MSX);
 	if(potential_platforms & TargetPlatform::Oric)			Append(Oric);
+	if(potential_platforms & TargetPlatform::Sega)			Append(Sega);
 	if(potential_platforms & TargetPlatform::ZX8081)		Append(ZX8081);
 	#undef Append
 

Analyser/Static/StaticAnalyser.hpp

@@ -11,9 +11,10 @@
 
 #include "../Machines.hpp"
 
-#include "../../Storage/Tape/Tape.hpp"
-#include "../../Storage/Disk/Disk.hpp"
 #include "../../Storage/Cartridge/Cartridge.hpp"
+#include "../../Storage/Disk/Disk.hpp"
+#include "../../Storage/MassStorage/MassStorageDevice.hpp"
+#include "../../Storage/Tape/Tape.hpp"
 
 #include <memory>
 #include <string>
@@ -29,9 +30,10 @@ struct Media {
 	std::vector<std::shared_ptr<Storage::Disk::Disk>> disks;
 	std::vector<std::shared_ptr<Storage::Tape::Tape>> tapes;
 	std::vector<std::shared_ptr<Storage::Cartridge::Cartridge>> cartridges;
+	std::vector<std::shared_ptr<Storage::MassStorage::MassStorageDevice>> mass_storage_devices;
 
 	bool empty() const {
-		return disks.empty() && tapes.empty() && cartridges.empty();
+		return disks.empty() && tapes.empty() && cartridges.empty() && mass_storage_devices.empty();
 	}
 };
 

ClockReceiver/ClockReceiver.hpp

@@ -9,6 +9,9 @@
 #ifndef ClockReceiver_hpp
 #define ClockReceiver_hpp
 
+#include "ForceInline.hpp"
+#include <cstdint>
+
 /*
 	Informal pattern for all classes that run from a clock cycle:
 
@@ -52,149 +55,193 @@
 */
 template <class T> class WrappedInt {
 	public:
-		constexpr WrappedInt(int l) : length_(l) {}
-		constexpr WrappedInt() : length_(0) {}
+		using IntType = int64_t;
 
-		T &operator =(const T &rhs) {
+		forceinline constexpr WrappedInt(IntType l) noexcept : length_(l) {}
+		forceinline constexpr WrappedInt() noexcept : length_(0) {}
+
+		forceinline T &operator =(const T &rhs) {
 			length_ = rhs.length_;
 			return *this;
 		}
 
-		T &operator +=(const T &rhs) {
+		forceinline T &operator +=(const T &rhs) {
 			length_ += rhs.length_;
 			return *static_cast<T *>(this);
 		}
 
-		T &operator -=(const T &rhs) {
+		forceinline T &operator -=(const T &rhs) {
 			length_ -= rhs.length_;
 			return *static_cast<T *>(this);
 		}
 
-		T &operator ++() {
+		forceinline T &operator ++() {
 			++ length_;
 			return *static_cast<T *>(this);
 		}
 
-		T &operator ++(int) {
+		forceinline T &operator ++(int) {
 			length_ ++;
 			return *static_cast<T *>(this);
 		}
 
-		T &operator --() {
+		forceinline T &operator --() {
 			-- length_;
 			return *static_cast<T *>(this);
 		}
 
-		T &operator --(int) {
+		forceinline T &operator --(int) {
 			length_ --;
 			return *static_cast<T *>(this);
 		}
 
-		T &operator %=(const T &rhs) {
+		forceinline T &operator *=(const T &rhs) {
+			length_ *= rhs.length_;
+			return *static_cast<T *>(this);
+		}
+
+		forceinline T &operator /=(const T &rhs) {
+			length_ /= rhs.length_;
+			return *static_cast<T *>(this);
+		}
+
+		forceinline T &operator %=(const T &rhs) {
 			length_ %= rhs.length_;
 			return *static_cast<T *>(this);
 		}
 
-		T &operator &=(const T &rhs) {
+		forceinline T &operator &=(const T &rhs) {
 			length_ &= rhs.length_;
 			return *static_cast<T *>(this);
 		}
 
-		constexpr T operator +(const T &rhs) const			{	return T(length_ + rhs.length_);	}
-		constexpr T operator -(const T &rhs) const			{	return T(length_ - rhs.length_);	}
+		forceinline constexpr T operator +(const T &rhs) const			{	return T(length_ + rhs.length_);	}
+		forceinline constexpr T operator -(const T &rhs) const			{	return T(length_ - rhs.length_);	}
 
-		constexpr T operator %(const T &rhs) const			{	return T(length_ % rhs.length_);	}
-		constexpr T operator &(const T &rhs) const			{	return T(length_ & rhs.length_);	}
+		forceinline constexpr T operator *(const T &rhs) const			{	return T(length_ * rhs.length_);	}
+		forceinline constexpr T operator /(const T &rhs) const			{	return T(length_ / rhs.length_);	}
 
-		constexpr T operator -() const						{	return T(- length_);				}
+		forceinline constexpr T operator %(const T &rhs) const			{	return T(length_ % rhs.length_);	}
+		forceinline constexpr T operator &(const T &rhs) const			{	return T(length_ & rhs.length_);	}
 
-		constexpr bool operator <(const T &rhs) const		{	return length_ < rhs.length_;		}
-		constexpr bool operator >(const T &rhs) const		{	return length_ > rhs.length_;		}
-		constexpr bool operator <=(const T &rhs) const		{	return length_ <= rhs.length_;		}
-		constexpr bool operator >=(const T &rhs) const		{	return length_ >= rhs.length_;		}
-		constexpr bool operator ==(const T &rhs) const		{	return length_ == rhs.length_;		}
-		constexpr bool operator !=(const T &rhs) const		{	return length_ != rhs.length_;		}
+		forceinline constexpr T operator -() const						{	return T(- length_);				}
 
-		constexpr bool operator !() const					{	return !length_;					}
+		forceinline constexpr bool operator <(const T &rhs) const		{	return length_ < rhs.length_;		}
+		forceinline constexpr bool operator >(const T &rhs) const		{	return length_ > rhs.length_;		}
+		forceinline constexpr bool operator <=(const T &rhs) const		{	return length_ <= rhs.length_;		}
+		forceinline constexpr bool operator >=(const T &rhs) const		{	return length_ >= rhs.length_;		}
+		forceinline constexpr bool operator ==(const T &rhs) const		{	return length_ == rhs.length_;		}
+		forceinline constexpr bool operator !=(const T &rhs) const		{	return length_ != rhs.length_;		}
+
+		forceinline constexpr bool operator !() const					{	return !length_;					}
 		// bool operator () is not supported because it offers an implicit cast to int, which is prone silently to permit misuse
 
-		constexpr int as_int() const { return length_; }
+		/// @returns The underlying int, cast to an integral type of your choosing.
+		template<typename Type = IntType> forceinline constexpr Type as() const { return Type(length_); }
+
+		/// @returns The underlying int, in its native form.
+		forceinline constexpr IntType as_integral() const { return length_; }
 
 		/*!
 			Severs from @c this the effect of dividing by @c divisor; @c this will end up with
 			the value of @c this modulo @c divisor and @c divided by @c divisor is returned.
 		*/
-		T divide(const T &divisor) {
-			T result(length_ / divisor.length_);
-			length_ %= divisor.length_;
-			return result;
+		template <typename Result = T> forceinline Result divide(const T &divisor) {
+			Result r;
+			static_cast<T *>(this)->fill(r, divisor);
+			return r;
 		}
 
 		/*!
 			Flushes the value in @c this. The current value is returned, and the internal value
 			is reset to zero.
 		*/
-		T flush() {
-			T result(length_);
-			length_ = 0;
-			return result;
+		template <typename Result> Result flush() {
+			// Jiggery pokery here; switching to function overloading avoids
+			// the namespace-level requirement for template specialisation.
+			Result r;
+			static_cast<T *>(this)->fill(r);
+			return r;
 		}
 
 		// operator int() is deliberately not provided, to avoid accidental subtitution of
 		// classes that use this template.
 
 	protected:
-		int length_;
+		IntType length_;
 };
 
 /// Describes an integer number of whole cycles: pairs of clock signal transitions.
 class Cycles: public WrappedInt<Cycles> {
 	public:
-		constexpr Cycles(int l) : WrappedInt<Cycles>(l) {}
-		constexpr Cycles() : WrappedInt<Cycles>() {}
-		constexpr Cycles(const Cycles &cycles) : WrappedInt<Cycles>(cycles.length_) {}
+		forceinline constexpr Cycles(IntType l) noexcept : WrappedInt<Cycles>(l) {}
+		forceinline constexpr Cycles() noexcept : WrappedInt<Cycles>() {}
+		forceinline constexpr Cycles(const Cycles &cycles) noexcept : WrappedInt<Cycles>(cycles.length_) {}
+
+	private:
+		friend WrappedInt;
+		void fill(Cycles &result) {
+			result.length_ = length_;
+			length_ = 0;
+		}
+
+		void fill(Cycles &result, const Cycles &divisor) {
+			result.length_ = length_ / divisor.length_;
+			length_ %= divisor.length_;
+		}
 };
 
 /// Describes an integer number of half cycles: single clock signal transitions.
 class HalfCycles: public WrappedInt<HalfCycles> {
 	public:
-		constexpr HalfCycles(int l) : WrappedInt<HalfCycles>(l) {}
-		constexpr HalfCycles() : WrappedInt<HalfCycles>() {}
+		forceinline constexpr HalfCycles(IntType l) noexcept : WrappedInt<HalfCycles>(l) {}
+		forceinline constexpr HalfCycles() noexcept : WrappedInt<HalfCycles>() {}
 
-		constexpr HalfCycles(const Cycles cycles) : WrappedInt<HalfCycles>(cycles.as_int() * 2) {}
-		constexpr HalfCycles(const HalfCycles &half_cycles) : WrappedInt<HalfCycles>(half_cycles.length_) {}
+		forceinline constexpr HalfCycles(const Cycles &cycles) noexcept : WrappedInt<HalfCycles>(cycles.as_integral() * 2) {}
+		forceinline constexpr HalfCycles(const HalfCycles &half_cycles) noexcept : WrappedInt<HalfCycles>(half_cycles.length_) {}
 
 		/// @returns The number of whole cycles completely covered by this span of half cycles.
-		constexpr Cycles cycles() const {
+		forceinline constexpr Cycles cycles() const {
 			return Cycles(length_ >> 1);
 		}
 
-		/// Flushes the whole cycles in @c this, subtracting that many from the total stored here.
-		Cycles flush_cycles() {
-			Cycles result(length_ >> 1);
-			length_ &= 1;
-			return result;
-		}
-
-		/// Flushes the half cycles in @c this, returning the number stored and setting this total to zero.
-		HalfCycles flush() {
-			HalfCycles result(length_);
-			length_ = 0;
-			return result;
-		}
-
 		/*!
 			Severs from @c this the effect of dividing by @c divisor; @c this will end up with
 			the value of @c this modulo @c divisor and @c divided by @c divisor is returned.
 		*/
-		Cycles divide_cycles(const Cycles &divisor) {
-			HalfCycles half_divisor = HalfCycles(divisor);
-			Cycles result(length_ / half_divisor.length_);
+		forceinline Cycles divide_cycles(const Cycles &divisor) {
+			const HalfCycles half_divisor = HalfCycles(divisor);
+			const Cycles result(length_ / half_divisor.length_);
 			length_ %= half_divisor.length_;
 			return result;
 		}
+
+	private:
+		friend WrappedInt;
+		void fill(Cycles &result) {
+			result = Cycles(length_ >> 1);
+			length_ &= 1;
+		}
+
+		void fill(HalfCycles &result) {
+			result.length_ = length_;
+			length_ = 0;
+		}
+
+		void fill(Cycles &result, const HalfCycles &divisor) {
+			result = Cycles(length_ / (divisor.length_ << 1));
+			length_ %= (divisor.length_ << 1);
+		}
+
+		void fill(HalfCycles &result, const HalfCycles &divisor) {
+			result.length_ = length_ / divisor.length_;
+			length_ %= divisor.length_;
+		}
 };
 
+// Create a specialisation of WrappedInt::flush for converting HalfCycles to Cycles
+// without losing the fractional part.
+
 /*!
 	If a component implements only run_for(Cycles), an owner can wrap it in HalfClockReceiver
 	automatically to gain run_for(HalfCycles).
@@ -203,9 +250,9 @@ template <class T> class HalfClockReceiver: public T {
 	public:
 		using T::T;
 
-		inline void run_for(const HalfCycles half_cycles) {
+		forceinline void run_for(const HalfCycles half_cycles) {
 			half_cycles_ += half_cycles;
-			T::run_for(half_cycles_.flush_cycles());
+			T::run_for(half_cycles_.flush<Cycles>());
 		}
 
 	private:

ClockReceiver/DeferredQueue.hpp

@@ -0,0 +1,82 @@
+//
+//  DeferredQueue.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 23/08/2018.
+//  Copyright © 2018 Thomas Harte. All rights reserved.
+//
+
+#ifndef DeferredQueue_h
+#define DeferredQueue_h
+
+#include <functional>
+#include <vector>
+
+/*!
+	A DeferredQueue maintains a list of ordered actions and the times at which
+	they should happen, and divides a total execution period up into the portions
+	that occur between those actions, triggering each action when it is reached.
+*/
+template <typename TimeUnit> class DeferredQueue {
+	public:
+		/// Constructs a DeferredQueue that will call target(period) in between deferred actions.
+		DeferredQueue(std::function<void(TimeUnit)> &&target) : target_(std::move(target)) {}
+
+		/*!
+			Schedules @c action to occur in @c delay units of time.
+
+			Actions must be scheduled in the order they will occur. It is undefined behaviour
+			to schedule them out of order.
+		*/
+		void defer(TimeUnit delay, const std::function<void(void)> &action) {
+			pending_actions_.emplace_back(delay, action);
+		}
+
+		/*!
+			Runs for @c length units of time.
+
+			The constructor-supplied target will be called with one or more periods that add up to @c length;
+			any scheduled actions will be called between periods.
+		*/
+		void run_for(TimeUnit length) {
+			// If there are no pending actions, just run for the entire length.
+			// This should be the normal branch.
+			if(pending_actions_.empty()) {
+				target_(length);
+				return;
+			}
+
+			// Divide the time to run according to the pending actions.
+			while(length > TimeUnit(0)) {
+				TimeUnit next_period = pending_actions_.empty() ? length : std::min(length, pending_actions_[0].delay);
+				target_(next_period);
+				length -= next_period;
+
+				off_t performances = 0;
+				for(auto &action: pending_actions_) {
+					action.delay -= next_period;
+					if(!action.delay) {
+						action.action();
+						++performances;
+					}
+				}
+				if(performances) {
+					pending_actions_.erase(pending_actions_.begin(), pending_actions_.begin() + performances);
+				}
+			}
+		}
+
+	private:
+		std::function<void(TimeUnit)> target_;
+
+		// The list of deferred actions.
+		struct DeferredAction {
+			TimeUnit delay;
+			std::function<void(void)> action;
+
+			DeferredAction(TimeUnit delay, const std::function<void(void)> &action) : delay(delay), action(std::move(action)) {}
+		};
+		std::vector<DeferredAction> pending_actions_;
+};
+
+#endif /* DeferredQueue_h */

ClockReceiver/ForceInline.hpp

@@ -9,9 +9,9 @@
 #ifndef ForceInline_hpp
 #define ForceInline_hpp
 
-#ifdef DEBUG
+#ifndef NDEBUG
 
-#define forceinline
+#define forceinline inline
 
 #else
 

ClockReceiver/JustInTime.hpp

@@ -0,0 +1,123 @@
+//
+//  JustInTime.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 28/07/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef JustInTime_h
+#define JustInTime_h
+
+#include "../Concurrency/AsyncTaskQueue.hpp"
+#include "ForceInline.hpp"
+
+/*!
+	A JustInTimeActor holds (i) an embedded object with a run_for method; and (ii) an amount
+	of time since run_for was last called.
+
+	Time can be added using the += operator. The -> operator can be used to access the
+	embedded object. All time accumulated will be pushed to object before the pointer is returned.
+
+	Machines that accumulate HalfCycle time but supply to a Cycle-counted device may supply a
+	separate @c TargetTimeScale at template declaration.
+*/
+template <class T, int multiplier = 1, int divider = 1, class LocalTimeScale = HalfCycles, class TargetTimeScale = LocalTimeScale> class JustInTimeActor {
+	public:
+		/// Constructs a new JustInTimeActor using the same construction arguments as the included object.
+		template<typename... Args> JustInTimeActor(Args&&... args) : object_(std::forward<Args>(args)...) {}
+
+		/// Adds time to the actor.
+		forceinline void operator += (const LocalTimeScale &rhs) {
+			if constexpr (multiplier != 1) {
+				time_since_update_ += rhs * multiplier;
+			} else {
+				time_since_update_ += rhs;
+			}
+			is_flushed_ = false;
+		}
+
+		/// Flushes all accumulated time and returns a pointer to the included object.
+		forceinline T *operator->() {
+			flush();
+			return &object_;
+		}
+
+		/// Returns a pointer to the included object without flushing time.
+		forceinline T *last_valid() {
+			return &object_;
+		}
+
+		/// Flushes all accumulated time.
+		forceinline void flush() {
+			if(!is_flushed_) {
+				is_flushed_ = true;
+				if constexpr (divider == 1) {
+					object_.run_for(time_since_update_.template flush<TargetTimeScale>());
+				} else {
+					const auto duration = time_since_update_.template divide<TargetTimeScale>(LocalTimeScale(divider));
+					if(duration > TargetTimeScale(0))
+						object_.run_for(duration);
+				}
+			}
+		}
+
+	private:
+		T object_;
+		LocalTimeScale time_since_update_;
+		bool is_flushed_ = true;
+};
+
+/*!
+	A AsyncJustInTimeActor acts like a JustInTimeActor but additionally contains an AsyncTaskQueue.
+	Any time the amount of accumulated time crosses a threshold provided at construction time,
+	the object will be updated on the AsyncTaskQueue.
+*/
+template <class T, class LocalTimeScale = HalfCycles, class TargetTimeScale = LocalTimeScale> class AsyncJustInTimeActor {
+	public:
+		/// Constructs a new AsyncJustInTimeActor using the same construction arguments as the included object.
+		template<typename... Args> AsyncJustInTimeActor(TargetTimeScale threshold, Args&&... args) :
+			object_(std::forward<Args>(args)...),
+		 	threshold_(threshold) {}
+
+		/// Adds time to the actor.
+		inline void operator += (const LocalTimeScale &rhs) {
+			time_since_update_ += rhs;
+			if(time_since_update_ >= threshold_) {
+				time_since_update_ -= threshold_;
+				task_queue_.enqueue([this] () {
+					object_.run_for(threshold_);
+				});
+			}
+			is_flushed_ = false;
+		}
+
+		/// Flushes all accumulated time and returns a pointer to the included object.
+		inline T *operator->() {
+			flush();
+			return &object_;
+		}
+
+		/// Returns a pointer to the included object without flushing time.
+		inline T *last_valid() {
+			return &object_;
+		}
+
+		/// Flushes all accumulated time.
+		inline void flush() {
+			if(!is_flushed_) {
+				task_queue_.flush();
+				object_.run_for(time_since_update_.template flush<TargetTimeScale>());
+				is_flushed_ = true;
+			}
+		}
+
+	private:
+		T object_;
+		LocalTimeScale time_since_update_;
+		TargetTimeScale threshold_;
+		bool is_flushed_ = true;
+		Concurrency::AsyncTaskQueue task_queue_;
+};
+
+#endif /* JustInTime_h */

Components/1770/1770.cpp

@@ -9,6 +9,8 @@
 #include "1770.hpp"
 
 #include "../../Storage/Disk/Encodings/MFM/Constants.hpp"
+
+#define LOG_PREFIX "[WD FDC] "
 #include "../../Outputs/Log.hpp"
 
 using namespace WD;
@@ -16,19 +18,19 @@ using namespace WD;
 WD1770::WD1770(Personality p) :
 		Storage::Disk::MFMController(8000000),
 		personality_(p),
-		interesting_event_mask_(static_cast<int>(Event1770::Command)) {
+		interesting_event_mask_(int(Event1770::Command)) {
 	set_is_double_density(false);
-	posit_event(static_cast<int>(Event1770::Command));
+	posit_event(int(Event1770::Command));
 }
 
-void WD1770::set_register(int address, uint8_t value) {
+void WD1770::write(int address, uint8_t value) {
 	switch(address&3) {
 		case 0: {
 			if((value&0xf0) == 0xd0) {
 				if(value == 0xd0) {
 					// Force interrupt **immediately**.
 					LOG("Force interrupt immediately");
-					posit_event(static_cast<int>(Event1770::ForceInterrupt));
+					posit_event(int(Event1770::ForceInterrupt));
 				} else {
 					ERROR("!!!TODO: force interrupt!!!");
 					update_status([] (Status &status) {
@@ -37,7 +39,7 @@ void WD1770::set_register(int address, uint8_t value) {
 				}
 			} else {
 				command_ = value;
-				posit_event(static_cast<int>(Event1770::Command));
+				posit_event(int(Event1770::Command));
 			}
 		}
 		break;
@@ -52,27 +54,35 @@ void WD1770::set_register(int address, uint8_t value) {
 	}
 }
 
-uint8_t WD1770::get_register(int address) {
+uint8_t WD1770::read(int address) {
 	switch(address&3) {
 		default: {
 			update_status([] (Status &status) {
 				status.interrupt_request = false;
 			});
 			uint8_t status =
-					(status_.write_protect ? Flag::WriteProtect : 0) |
-					(status_.crc_error ? Flag::CRCError : 0) |
-					(status_.busy ? Flag::Busy : 0);
+				(status_.crc_error ? Flag::CRCError : 0) |
+				(status_.busy ? Flag::Busy : 0);
+
+			// Per Jean Louis-Guérin's documentation:
+			//
+			//	* 	the write-protect bit is locked into place by a type 2 or type 3 command, but is
+			//		read live after a type 1.
+			//	*	the track 0 bit is captured during a type 1 instruction and lost upon any other type,
+			//		it is not live sampled.
 			switch(status_.type) {
 				case Status::One:
 					status |=
-						(get_drive().get_is_track_zero() ? Flag::TrackZero : 0) |
-						(status_.seek_error ? Flag::SeekError : 0);
-						// TODO: index hole
+						(status_.track_zero ? Flag::TrackZero : 0) |
+						(status_.seek_error ? Flag::SeekError : 0) |
+						(get_drive().get_is_read_only() ? Flag::WriteProtect : 0) |
+						(get_drive().get_index_pulse() ? Flag::Index : 0);
 				break;
 
 				case Status::Two:
 				case Status::Three:
 					status |=
+						(status_.write_protect ? Flag::WriteProtect : 0) |
 						(status_.record_type ? Flag::RecordType : 0) |
 						(status_.lost_data ? Flag::LostData : 0) |
 						(status_.data_request ? Flag::DataRequest : 0) |
@@ -89,10 +99,15 @@ uint8_t WD1770::get_register(int address) {
 				if(status_.type == Status::One)
 					status |= (status_.spin_up ? Flag::SpinUp : 0);
 			}
+//			LOG("Returned status " << PADHEX(2) << int(status) << " of type " << 1+int(status_.type));
 			return status;
 		}
-		case 1:		return track_;
-		case 2:		return sector_;
+		case 1:
+			LOG("Returned track " << int(track_));
+			return track_;
+		case 2:
+			LOG("Returned sector " << int(sector_));
+			return sector_;
 		case 3:
 			update_status([] (Status &status) {
 				status.data_request = false;
@@ -105,28 +120,30 @@ void WD1770::run_for(const Cycles cycles) {
 	Storage::Disk::Controller::run_for(cycles);
 
 	if(delay_time_) {
-		unsigned int number_of_cycles = static_cast<unsigned int>(cycles.as_int());
+		const auto number_of_cycles = cycles.as_integral();
 		if(delay_time_ <= number_of_cycles) {
 			delay_time_ = 0;
-			posit_event(static_cast<int>(Event1770::Timer));
+			posit_event(int(Event1770::Timer));
 		} else {
 			delay_time_ -= number_of_cycles;
 		}
 	}
 }
 
-#define WAIT_FOR_EVENT(mask)	resume_point_ = __LINE__; interesting_event_mask_ = static_cast<int>(mask); return; case __LINE__:
+#define WAIT_FOR_EVENT(mask)	resume_point_ = __LINE__; interesting_event_mask_ = int(mask); return; case __LINE__:
 #define WAIT_FOR_TIME(ms)		resume_point_ = __LINE__; delay_time_ = ms * 8000; WAIT_FOR_EVENT(Event1770::Timer);
-#define WAIT_FOR_BYTES(count)	resume_point_ = __LINE__; distance_into_section_ = 0; WAIT_FOR_EVENT(Event::Token); if(get_latest_token().type == Token::Byte) distance_into_section_++; if(distance_into_section_ < count) { interesting_event_mask_ = static_cast<int>(Event::Token); return; }
+#define WAIT_FOR_BYTES(count)	resume_point_ = __LINE__; distance_into_section_ = 0; WAIT_FOR_EVENT(Event::Token); if(get_latest_token().type == Token::Byte) distance_into_section_++; if(distance_into_section_ < count) { interesting_event_mask_ = int(Event::Token); return; }
 #define BEGIN_SECTION()	switch(resume_point_) { default:
 #define END_SECTION()	(void)0; }
 
 #define READ_ID()	\
-		if(new_event_type == static_cast<int>(Event::Token)) {	\
-			if(!distance_into_section_ && get_latest_token().type == Token::ID) {set_data_mode(DataMode::Reading); distance_into_section_++; }	\
-			else if(distance_into_section_ && distance_into_section_ < 7 && get_latest_token().type == Token::Byte) {	\
+		if(new_event_type == int(Event::Token)) {	\
+			if(!distance_into_section_ && get_latest_token().type == Token::ID) {\
+				set_data_mode(DataMode::Reading);	\
+				++distance_into_section_;	\
+			} else if(distance_into_section_ && distance_into_section_ < 7 && get_latest_token().type == Token::Byte) {	\
 				header_[distance_into_section_ - 1] = get_latest_token().byte_value;	\
-				distance_into_section_++;	\
+				++distance_into_section_;	\
 			}	\
 		}
 
@@ -141,28 +158,28 @@ void WD1770::run_for(const Cycles cycles) {
 		WAIT_FOR_EVENT(Event1770::IndexHoleTarget);	\
 		status_.spin_up = true;
 
-//     +--------+----------+-------------------------+
-//     !	    !	       !          BITS           !
-//     ! TYPE   ! COMMAND  !  7  6	5  4  3  2  1  0 !
-//     +--------+----------+-------------------------+
-//     !	 1  ! Restore  !  0  0	0  0  h  v r1 r0 !
-//     !	 1  ! Seek     !  0  0	0  1  h  v r1 r0 !
-//     !	 1  ! Step     !  0  0	1  u  h  v r1 r0 !
-//     !	 1  ! Step-in  !  0  1	0  u  h  v r1 r0 !
-//     !	 1  ! Step-out !  0  1	1  u  h  v r1 r0 !
-//     !	 2  ! Rd sectr !  1  0	0  m  h  E  0  0 !
-//     !	 2  ! Wt sectr !  1  0	1  m  h  E  P a0 !
-//     !	 3  ! Rd addr  !  1  1	0  0  h  E  0  0 !
-//     !	 3  ! Rd track !  1  1	1  0  h  E  0  0 !
-//     !	 3  ! Wt track !  1  1	1  1  h  E  P  0 !
-//     !	 4  ! Forc int !  1  1	0  1 i3 i2 i1 i0 !
-//     +--------+----------+-------------------------+
+// +--------+----------+-------------------------+
+// !	    !	       !          BITS           !
+// ! TYPE   ! COMMAND  !  7  6	5  4  3  2  1  0 !
+// +--------+----------+-------------------------+
+// !	 1  ! Restore  !  0  0	0  0  h  v r1 r0 !
+// !	 1  ! Seek     !  0  0	0  1  h  v r1 r0 !
+// !	 1  ! Step     !  0  0	1  u  h  v r1 r0 !
+// !	 1  ! Step-in  !  0  1	0  u  h  v r1 r0 !
+// !	 1  ! Step-out !  0  1	1  u  h  v r1 r0 !
+// !	 2  ! Rd sectr !  1  0	0  m  h  E  0  0 !
+// !	 2  ! Wt sectr !  1  0	1  m  h  E  P a0 !
+// !	 3  ! Rd addr  !  1  1	0  0  h  E  0  0 !
+// !	 3  ! Rd track !  1  1	1  0  h  E  0  0 !
+// !	 3  ! Wt track !  1  1	1  1  h  E  P  0 !
+// !	 4  ! Forc int !  1  1	0  1 i3 i2 i1 i0 !
+// +--------+----------+-------------------------+
 
 void WD1770::posit_event(int new_event_type) {
-	if(new_event_type == static_cast<int>(Event::IndexHole)) {
+	if(new_event_type == int(Event::IndexHole)) {
 		index_hole_count_++;
 		if(index_hole_count_target_ == index_hole_count_) {
-			posit_event(static_cast<int>(Event1770::IndexHoleTarget));
+			posit_event(int(Event1770::IndexHoleTarget));
 			index_hole_count_target_ = -1;
 		}
 
@@ -177,19 +194,19 @@ void WD1770::posit_event(int new_event_type) {
 		}
 	}
 
-	if(new_event_type == static_cast<int>(Event1770::ForceInterrupt)) {
+	if(new_event_type == int(Event1770::ForceInterrupt)) {
 		interesting_event_mask_ = 0;
 		resume_point_ = 0;
 		update_status([] (Status &status) {
 			status.type = Status::One;
 			status.data_request = false;
+			status.spin_up = false;
 		});
 	} else {
-		if(!(interesting_event_mask_ & static_cast<int>(new_event_type))) return;
+		if(!(interesting_event_mask_ & int(new_event_type))) return;
 		interesting_event_mask_ &= ~new_event_type;
 	}
 
-	Status new_status;
 	BEGIN_SECTION()
 
 	// Wait for a new command, branch to the appropriate handler.
@@ -209,9 +226,10 @@ void WD1770::posit_event(int new_event_type) {
 		update_status([] (Status &status) {
 			status.busy = true;
 			status.interrupt_request = false;
+			status.track_zero = false;	// Always reset by a non-type 1; so reset regardless and set properly later.
 		});
 
-		LOG("Starting " << std::hex << command_ << std::endl);
+		LOG("Starting " << PADHEX(2) << int(command_));
 
 		if(!(command_ & 0x80)) goto begin_type_1;
 		if(!(command_ & 0x40)) goto begin_type_2;
@@ -221,16 +239,16 @@ void WD1770::posit_event(int new_event_type) {
 	/*
 		Type 1 entry point.
 	*/
-//     +--------+----------+-------------------------+
-//     !	    !	       !          BITS           !
-//     ! TYPE   ! COMMAND  !  7  6	5  4  3  2  1  0 !
-//     +--------+----------+-------------------------+
-//     !	 1  ! Restore  !  0  0	0  0  h  v r1 r0 !
-//     !	 1  ! Seek     !  0  0	0  1  h  v r1 r0 !
-//     !	 1  ! Step     !  0  0	1  u  h  v r1 r0 !
-//     !	 1  ! Step-in  !  0  1	0  u  h  v r1 r0 !
-//     !	 1  ! Step-out !  0  1	1  u  h  v r1 r0 !
-//     +--------+----------+-------------------------+
+	// +--------+----------+-------------------------+
+	// !	    !	       !          BITS           !
+	// ! TYPE   ! COMMAND  !  7  6	5  4  3  2  1  0 !
+	// +--------+----------+-------------------------+
+	// !	 1  ! Restore  !  0  0	0  0  h  v r1 r0 !
+	// !	 1  ! Seek     !  0  0	0  1  h  v r1 r0 !
+	// !	 1  ! Step     !  0  0	1  u  h  v r1 r0 !
+	// !	 1  ! Step-in  !  0  1	0  u  h  v r1 r0 !
+	// !	 1  ! Step-out !  0  1	1  u  h  v r1 r0 !
+	// +--------+----------+-------------------------+
 
 	begin_type_1:
 		// Set initial flags, skip spin-up if possible.
@@ -241,6 +259,7 @@ void WD1770::posit_event(int new_event_type) {
 			status.data_request = false;
 		});
 
+		LOG("Step/Seek/Restore with track " << int(track_) << " data " << int(data_));
 		if(!has_motor_on_line() && !has_head_load_line()) goto test_type1_type;
 
 		if(has_motor_on_line()) goto begin_type1_spin_up;
@@ -273,19 +292,19 @@ void WD1770::posit_event(int new_event_type) {
 		}
 
 	perform_seek_or_restore_command:
-		if(track_ == data_) goto verify;
+		if(track_ == data_) goto verify_seek;
 		step_direction_ = (data_ > track_);
 
 	adjust_track:
-		if(step_direction_) track_++; else track_--;
+		if(step_direction_) ++track_; else --track_;
 
 	perform_step:
 		if(!step_direction_ && get_drive().get_is_track_zero()) {
 			track_ = 0;
-			goto verify;
+			goto verify_seek;
 		}
 		get_drive().step(Storage::Disk::HeadPosition(step_direction_ ? 1 : -1));
-		unsigned int time_to_wait;
+		Cycles::IntType time_to_wait;
 		switch(command_ & 3) {
 			default:
 			case 0: time_to_wait = 6;	break;
@@ -294,14 +313,17 @@ void WD1770::posit_event(int new_event_type) {
 			case 3: time_to_wait = (personality_ == P1772) ? 3 : 30;	break;
 		}
 		WAIT_FOR_TIME(time_to_wait);
-		if(command_ >> 5) goto verify;
+		if(command_ >> 5) goto verify_seek;
 		goto perform_seek_or_restore_command;
 
 	perform_step_command:
 		if(command_ & 0x10) goto adjust_track;
 		goto perform_step;
 
-	verify:
+	verify_seek:
+		update_status([this] (Status &status) {
+			status.track_zero = get_drive().get_is_track_zero();
+		});
 		if(!(command_ & 0x04)) {
 			goto wait_for_command;
 		}
@@ -310,17 +332,20 @@ void WD1770::posit_event(int new_event_type) {
 		distance_into_section_ = 0;
 
 	verify_read_data:
-		WAIT_FOR_EVENT(static_cast<int>(Event::IndexHole) | static_cast<int>(Event::Token));
+		WAIT_FOR_EVENT(int(Event::IndexHole) | int(Event::Token));
 		READ_ID();
 
 		if(index_hole_count_ == 6) {
+			LOG("Nothing found to verify");
 			update_status([] (Status &status) {
 				status.seek_error = true;
 			});
 			goto wait_for_command;
 		}
 		if(distance_into_section_ == 7) {
+			distance_into_section_ = 0;
 			set_data_mode(DataMode::Scanning);
+
 			if(get_crc_generator().get_value()) {
 				update_status([] (Status &status) {
 					status.crc_error = true;
@@ -329,14 +354,12 @@ void WD1770::posit_event(int new_event_type) {
 			}
 
 			if(header_[0] == track_) {
-				LOG("Reached track " << std::dec << track_);
+				LOG("Reached track " << std::dec << int(track_));
 				update_status([] (Status &status) {
 					status.crc_error = false;
 				});
 				goto wait_for_command;
 			}
-
-			distance_into_section_ = 0;
 		}
 		goto verify_read_data;
 
@@ -344,13 +367,13 @@ void WD1770::posit_event(int new_event_type) {
 	/*
 		Type 2 entry point.
 	*/
-//     +--------+----------+-------------------------+
-//     !	    !	       !          BITS           !
-//     ! TYPE   ! COMMAND  !  7  6	5  4  3  2  1  0 !
-//     +--------+----------+-------------------------+
-//     !	 2  ! Rd sectr !  1  0	0  m  h  E  0  0 !
-//     !	 2  ! Wt sectr !  1  0	1  m  h  E  P a0 !
-//     +--------+----------+-------------------------+
+	// +--------+----------+-------------------------+
+	// !	    !	       !          BITS           !
+	// ! TYPE   ! COMMAND  !  7  6	5  4  3  2  1  0 !
+	// +--------+----------+-------------------------+
+	// !	 2  ! Rd sectr !  1  0	0  m  h  E  0  0 !
+	// !	 2  ! Wt sectr !  1  0	1  m  h  E  P a0 !
+	// +--------+----------+-------------------------+
 
 	begin_type_2:
 		update_status([] (Status &status) {
@@ -393,23 +416,28 @@ void WD1770::posit_event(int new_event_type) {
 			goto wait_for_command;
 		}
 
+		distance_into_section_ = 0;
+		set_data_mode(DataMode::Scanning);
+
 	type2_get_header:
-		WAIT_FOR_EVENT(static_cast<int>(Event::IndexHole) | static_cast<int>(Event::Token));
+		WAIT_FOR_EVENT(int(Event::IndexHole) | int(Event::Token));
 		READ_ID();
 
 		if(index_hole_count_ == 5) {
-			LOG("Failed to find sector " << std::dec << sector_);
+			LOG("Failed to find sector " << std::dec << int(sector_));
 			update_status([] (Status &status) {
 				status.record_not_found = true;
 			});
 			goto wait_for_command;
 		}
 		if(distance_into_section_ == 7) {
-			LOG("Considering " << std::dec << header_[0] << "/" << header_[2]);
+			distance_into_section_ = 0;
 			set_data_mode(DataMode::Scanning);
+
+			LOG("Considering " << std::dec << int(header_[0]) << "/" << int(header_[2]));
 			if(		header_[0] == track_ && header_[2] == sector_ &&
 					(has_motor_on_line() || !(command_&0x02) || ((command_&0x08) >> 3) == header_[1])) {
-				LOG("Found " << std::dec << header_[0] << "/" << header_[2]);
+				LOG("Found " << std::dec << int(header_[0]) << "/" << int(header_[2]));
 				if(get_crc_generator().get_value()) {
 					LOG("CRC error; back to searching");
 					update_status([] (Status &status) {
@@ -423,7 +451,6 @@ void WD1770::posit_event(int new_event_type) {
 				});
 				goto type2_read_or_write_data;
 			}
-			distance_into_section_ = 0;
 		}
 		goto type2_get_header;
 
@@ -466,6 +493,9 @@ void WD1770::posit_event(int new_event_type) {
 		header_[distance_into_section_] = get_latest_token().byte_value;
 		distance_into_section_++;
 		if(distance_into_section_ == 2) {
+			distance_into_section_ = 0;
+			set_data_mode(DataMode::Scanning);
+
 			if(get_crc_generator().get_value()) {
 				LOG("CRC error; terminating");
 				update_status([this] (Status &status) {
@@ -474,11 +504,13 @@ void WD1770::posit_event(int new_event_type) {
 				goto wait_for_command;
 			}
 
+			LOG("Finished reading sector " << std::dec << int(sector_));
+
 			if(command_ & 0x10) {
 				sector_++;
+				LOG("Advancing to search for sector " << std::dec << int(sector_));
 				goto test_type2_write_protection;
 			}
-			LOG("Finished reading sector " << std::dec << sector_);
 			goto wait_for_command;
 		}
 		goto type2_check_crc;
@@ -560,21 +592,21 @@ void WD1770::posit_event(int new_event_type) {
 			sector_++;
 			goto test_type2_write_protection;
 		}
-		LOG("Wrote sector " << std::dec << sector_);
+		LOG("Wrote sector " << std::dec << int(sector_));
 		goto wait_for_command;
 
 
 	/*
 		Type 3 entry point.
 	*/
-//     +--------+----------+-------------------------+
-//     !	    !	       !          BITS           !
-//     ! TYPE   ! COMMAND  !  7  6	5  4  3  2  1  0 !
-//     +--------+----------+-------------------------+
-//     !	 3  ! Rd addr  !  1  1	0  0  h  E  0  0 !
-//     !	 3  ! Rd track !  1  1	1  0  h  E  0  0 !
-//     !	 3  ! Wt track !  1  1	1  1  h  E  P  0 !
-//     +--------+----------+-------------------------+
+	// +--------+----------+-------------------------+
+	// !	    !	       !          BITS           !
+	// ! TYPE   ! COMMAND  !  7  6	5  4  3  2  1  0 !
+	// +--------+----------+-------------------------+
+	// !	 3  ! Rd addr  !  1  1	0  0  h  E  0  0 !
+	// !	 3  ! Rd track !  1  1	1  0  h  E  0  0 !
+	// !	 3  ! Wt track !  1  1	1  1  h  E  P  0 !
+	// +--------+----------+-------------------------+
 	begin_type_3:
 		update_status([] (Status &status) {
 			status.type = Status::Three;
@@ -611,8 +643,8 @@ void WD1770::posit_event(int new_event_type) {
 		distance_into_section_ = 0;
 
 	read_address_get_header:
-		WAIT_FOR_EVENT(static_cast<int>(Event::IndexHole) | static_cast<int>(Event::Token));
-		if(new_event_type == static_cast<int>(Event::Token)) {
+		WAIT_FOR_EVENT(int(Event::IndexHole) | int(Event::Token));
+		if(new_event_type == int(Event::Token)) {
 			if(!distance_into_section_ && get_latest_token().type == Token::ID) {set_data_mode(DataMode::Reading); distance_into_section_++; }
 			else if(distance_into_section_ && distance_into_section_ < 7 && get_latest_token().type == Token::Byte) {
 				if(status_.data_request) {
@@ -626,9 +658,11 @@ void WD1770::posit_event(int new_event_type) {
 				update_status([] (Status &status) {
 					status.data_request = true;
 				});
-				distance_into_section_++;
+				++distance_into_section_;
 
 				if(distance_into_section_ == 7) {
+					distance_into_section_ = 0;
+
 					if(get_crc_generator().get_value()) {
 						update_status([] (Status &status) {
 							status.crc_error = true;
@@ -652,7 +686,7 @@ void WD1770::posit_event(int new_event_type) {
 		index_hole_count_ = 0;
 
 	read_track_read_byte:
-		WAIT_FOR_EVENT(static_cast<int>(Event::Token) | static_cast<int>(Event::IndexHole));
+		WAIT_FOR_EVENT(int(Event::Token) | int(Event::IndexHole));
 		if(index_hole_count_) {
 			goto wait_for_command;
 		}
@@ -719,7 +753,7 @@ void WD1770::posit_event(int new_event_type) {
 				case 0xfd: case 0xfe:
 					// clock is 0xc7 = 1010 0000 0010 1010 = 0xa022
 					write_raw_short(
-						static_cast<uint16_t>(
+						uint16_t(
 							0xa022 |
 							((data_ & 0x80) << 7) |
 							((data_ & 0x40) << 6) |
@@ -768,15 +802,18 @@ void WD1770::posit_event(int new_event_type) {
 }
 
 void WD1770::update_status(std::function<void(Status &)> updater) {
+	const Status old_status = status_;
+
 	if(delegate_) {
-		Status old_status = status_;
 		updater(status_);
-		bool did_change =
+		const bool did_change =
 			(status_.busy != old_status.busy) ||
-			(status_.data_request != old_status.data_request);
+			(status_.data_request != old_status.data_request) ||
+			(status_.interrupt_request != old_status.interrupt_request);
 		if(did_change) delegate_->wd1770_did_change_output(this);
-	}
-	else updater(status_);
+	} else updater(status_);
+
+	if(status_.busy != old_status.busy) update_clocking_observer();
 }
 
 void WD1770::set_head_load_request(bool head_load) {}
@@ -784,5 +821,14 @@ void WD1770::set_motor_on(bool motor_on) {}
 
 void WD1770::set_head_loaded(bool head_loaded) {
 	head_is_loaded_ = head_loaded;
-	if(head_loaded) posit_event(static_cast<int>(Event1770::HeadLoad));
+	if(head_loaded) posit_event(int(Event1770::HeadLoad));
+}
+
+bool WD1770::get_head_loaded() {
+	return head_is_loaded_;
+}
+
+ClockingHint::Preference WD1770::preferred_clocking() {
+	if(status_.busy) return ClockingHint::Preference::RealTime;
+	return Storage::Disk::MFMController::preferred_clocking();
 }

Components/1770/1770.hpp

@@ -36,10 +36,10 @@ class WD1770: public Storage::Disk::MFMController {
 		using Storage::Disk::MFMController::set_is_double_density;
 
 		/// Writes @c value to the register at @c address. Only the low two bits of the address are decoded.
-		void set_register(int address, uint8_t value);
+		void write(int address, uint8_t value);
 
 		/// Fetches the value of the register @c address. Only the low two bits of the address are decoded.
-		uint8_t get_register(int address);
+		uint8_t read(int address);
 
 		/// Runs the controller for @c number_of_cycles cycles.
 		void run_for(const Cycles cycles);
@@ -73,11 +73,16 @@ class WD1770: public Storage::Disk::MFMController {
 		};
 		inline void set_delegate(Delegate *delegate)	{	delegate_ = delegate;			}
 
+		ClockingHint::Preference preferred_clocking() final;
+
 	protected:
 		virtual void set_head_load_request(bool head_load);
 		virtual void set_motor_on(bool motor_on);
 		void set_head_loaded(bool head_loaded);
 
+		/// @returns The last value posted to @c set_head_loaded.
+		bool get_head_loaded();
+
 	private:
 		Personality personality_;
 		inline bool has_motor_on_line() { return (personality_ != P1793 ) && (personality_ != P1773); }
@@ -94,6 +99,7 @@ class WD1770: public Storage::Disk::MFMController {
 			bool data_request = false;
 			bool interrupt_request = false;
 			bool busy = false;
+			bool track_zero = false;
 			enum {
 				One, Two, Three
 			} type = One;
@@ -121,7 +127,7 @@ class WD1770: public Storage::Disk::MFMController {
 		void posit_event(int type);
 		int interesting_event_mask_;
 		int resume_point_ = 0;
-		unsigned int delay_time_ = 0;
+		Cycles::IntType delay_time_ = 0;
 
 		// ID buffer
 		uint8_t header_[6];

Components/5380/ncr5380.cpp

@@ -0,0 +1,312 @@
+//
+//  ncr5380.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 10/08/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "ncr5380.hpp"
+
+#include "../../Outputs/Log.hpp"
+
+using namespace NCR::NCR5380;
+using SCSI::Line;
+
+NCR5380::NCR5380(SCSI::Bus &bus, int clock_rate) :
+	bus_(bus),
+	clock_rate_(clock_rate) {
+	device_id_ = bus_.add_device();
+	bus_.add_observer(this);
+}
+
+void NCR5380::write(int address, uint8_t value, bool dma_acknowledge) {
+	switch(address & 7) {
+		case 0:
+//			LOG("[SCSI 0] Set current SCSI bus state to " << PADHEX(2) << int(value));
+			data_bus_ = value;
+
+			if(dma_request_ && dma_operation_ == DMAOperation::Send) {
+//				printf("w %02x\n", value);
+				dma_acknowledge_ = true;
+				dma_request_ = false;
+				update_control_output();
+				bus_.set_device_output(device_id_, bus_output_);
+			}
+		break;
+
+		case 1: {
+//			LOG("[SCSI 1] Initiator command register set: " << PADHEX(2) << int(value));
+			initiator_command_ = value;
+
+			bus_output_ &= ~(Line::Reset | Line::Acknowledge | Line::Busy | Line::SelectTarget | Line::Attention);
+			if(value & 0x80) bus_output_ |= Line::Reset;
+			if(value & 0x08) bus_output_ |= Line::Busy;
+			if(value & 0x04) bus_output_ |= Line::SelectTarget;
+
+			/* bit 5 = differential enable if this were a 5381 */
+
+			test_mode_ = value & 0x40;
+			assert_data_bus_ = value & 0x01;
+			update_control_output();
+		} break;
+
+		case 2:
+//			LOG("[SCSI 2] Set mode: " << PADHEX(2) << int(value));
+			mode_ = value;
+
+			// bit 7: 1 = use block mode DMA mode (if DMA mode is also enabled)
+			// bit 6: 1 = be a SCSI target; 0 = be an initiator
+			// bit 5: 1 = check parity
+			// bit 4: 1 = generate an interrupt if parity checking is enabled and an error is found
+			// bit 3: 1 = generate an interrupt when an EOP is received from the DMA controller
+			// bit 2: 1 = generate an interrupt and reset low 6 bits of register 1 if an unexpected loss of Line::Busy occurs
+			// bit 1: 1 = use DMA mode
+			// bit 0: 1 = begin arbitration mode (device ID should be in register 0)
+			arbitration_in_progress_ = false;
+			switch(mode_ & 0x3) {
+				case 0x0:
+					bus_output_ &= ~SCSI::Line::Busy;
+					dma_request_ = false;
+					set_execution_state(ExecutionState::None);
+				break;
+
+				case 0x1:
+					arbitration_in_progress_ = true;
+					set_execution_state(ExecutionState::WaitingForBusy);
+					lost_arbitration_ = false;
+				break;
+
+				default:
+					assert_data_bus_ = false;
+					set_execution_state(ExecutionState::PerformingDMA);
+					bus_.update_observers();
+				break;
+			}
+			update_control_output();
+		break;
+
+		case 3: {
+//			LOG("[SCSI 3] Set target command: " << PADHEX(2) << int(value));
+			target_command_ = value;
+			update_control_output();
+		} break;
+
+		case 4:
+//			LOG("[SCSI 4] Set select enabled: " << PADHEX(2) << int(value));
+		break;
+
+		case 5:
+//			LOG("[SCSI 5] Start DMA send: " << PADHEX(2) << int(value));
+			dma_operation_ = DMAOperation::Send;
+		break;
+
+		case 6:
+//			LOG("[SCSI 6] Start DMA target receive: " << PADHEX(2) << int(value));
+			dma_operation_ = DMAOperation::TargetReceive;
+		break;
+
+		case 7:
+//			LOG("[SCSI 7] Start DMA initiator receive: " << PADHEX(2) << int(value));
+			dma_operation_ = DMAOperation::InitiatorReceive;
+		break;
+	}
+
+	// Data is output only if the data bus is asserted.
+	if(assert_data_bus_) {
+		bus_output_ = (bus_output_ & ~SCSI::Line::Data) | data_bus_;
+	} else {
+		bus_output_ &= ~SCSI::Line::Data;
+	}
+
+	// In test mode, still nothing is output. Otherwise throw out
+	// the current value of bus_output_.
+	if(test_mode_) {
+		bus_.set_device_output(device_id_, SCSI::DefaultBusState);
+	} else {
+		bus_.set_device_output(device_id_, bus_output_);
+	}
+}
+
+uint8_t NCR5380::read(int address, bool dma_acknowledge) {
+	switch(address & 7) {
+		case 0:
+//			LOG("[SCSI 0] Get current SCSI bus state: " << PADHEX(2) << (bus_.get_state() & 0xff));
+
+			if(dma_request_ && dma_operation_ == DMAOperation::InitiatorReceive) {
+				dma_acknowledge_ = true;
+				dma_request_ = false;
+				update_control_output();
+				bus_.set_device_output(device_id_, bus_output_);
+			}
+		return uint8_t(bus_.get_state());
+
+		case 1:
+//			LOG("[SCSI 1] Initiator command register get: " << (arbitration_in_progress_ ? 'p' : '-') <<  (lost_arbitration_ ? 'l' : '-'));
+		return
+			// Bits repeated as they were set.
+			(initiator_command_ & ~0x60) |
+
+			// Arbitration in progress.
+			(arbitration_in_progress_ ? 0x40 : 0x00) |
+
+			// Lost arbitration.
+			(lost_arbitration_ ? 0x20 : 0x00);
+
+		case 2:
+//			LOG("[SCSI 2] Get mode");
+		return mode_;
+
+		case 3:
+//			LOG("[SCSI 3] Get target command");
+		return target_command_;
+
+		case 4: {
+			const auto bus_state = bus_.get_state();
+			const uint8_t result =
+				((bus_state & Line::Reset)			? 0x80 : 0x00) |
+				((bus_state & Line::Busy)			? 0x40 : 0x00) |
+				((bus_state & Line::Request)		? 0x20 : 0x00) |
+				((bus_state & Line::Message)		? 0x10 : 0x00) |
+				((bus_state & Line::Control)		? 0x08 : 0x00) |
+				((bus_state & Line::Input)			? 0x04 : 0x00) |
+				((bus_state & Line::SelectTarget)	? 0x02 : 0x00) |
+				((bus_state & Line::Parity)			? 0x01 : 0x00);
+//			LOG("[SCSI 4] Get current bus state: " << PADHEX(2) << int(result));
+			return result;
+		}
+
+		case 5: {
+			const auto bus_state = bus_.get_state();
+			const bool phase_matches =
+				(target_output() & (Line::Message | Line::Control | Line::Input)) ==
+				(bus_state & (Line::Message | Line::Control | Line::Input));
+
+			const uint8_t result =
+				/* b7 = end of DMA */
+				((dma_request_ && state_ == ExecutionState::PerformingDMA) ? 0x40 : 0x00)	|
+				/* b5 = parity error */
+				/* b4 = IRQ active */
+				(phase_matches ? 0x08 : 0x00)	|
+				/* b2 = busy error */
+				((bus_state & Line::Attention) ? 0x02 : 0x00) |
+				((bus_state & Line::Acknowledge) ? 0x01 : 0x00);
+//			LOG("[SCSI 5] Get bus and status: " << PADHEX(2) << int(result));
+			return result;
+		}
+
+		case 6:
+//			LOG("[SCSI 6] Get input data");
+		return 0xff;
+
+		case 7:
+//			LOG("[SCSI 7] Reset parity/interrupt");
+		return 0xff;
+	}
+	return 0;
+}
+
+SCSI::BusState NCR5380::target_output() {
+	SCSI::BusState output = SCSI::DefaultBusState;
+	if(target_command_ & 0x08) output |= Line::Request;
+	if(target_command_ & 0x04) output |= Line::Message;
+	if(target_command_ & 0x02) output |= Line::Control;
+	if(target_command_ & 0x01) output |= Line::Input;
+	return output;
+}
+
+void NCR5380::update_control_output() {
+	bus_output_ &= ~(Line::Request | Line::Message | Line::Control | Line::Input | Line::Acknowledge | Line::Attention);
+	if(mode_ & 0x40) {
+		// This is a target; C/D, I/O, /MSG and /REQ are signalled on the bus.
+		bus_output_ |= target_output();
+	} else {
+		// This is an initiator; /ATN and /ACK are signalled on the bus.
+		if(
+			(initiator_command_ & 0x10) ||
+			(state_ == ExecutionState::PerformingDMA && dma_acknowledge_)
+		) bus_output_ |= Line::Acknowledge;
+		if(initiator_command_ & 0x02) bus_output_ |= Line::Attention;
+	}
+}
+
+void NCR5380::scsi_bus_did_change(SCSI::Bus *, SCSI::BusState new_state, double time_since_change) {
+	switch(state_) {
+		default: break;
+
+		/*
+			Official documentation:
+
+				Arbitration is accomplished using a bus-free filter to continuously monitor BSY.
+				If BSY remains inactive for at least 400 nsec then the SCSI bus is considered free
+				and arbitration may begin. Arbitration will begin if the bus is free, SEL is inactive
+				and the ARBITRATION bit (port 2, bit 0) is active. Once arbitration has begun
+				(BSY asserted), an arbitration delay of 2.2 /Lsec must elapse before the data bus
+				can be examined to deter- mine if arbitration has been won. This delay must be
+				implemented in the controlling software driver.
+
+			Personal notes:
+
+				I'm discounting that "arbitratation is accomplished" opening, and assuming that what needs
+				to happen is:
+
+					(i) wait for BSY to be inactive;
+					(ii) count 400 nsec;
+					(iii) check that BSY and SEL are inactive.
+		*/
+
+		case ExecutionState::WaitingForBusy:
+			if(!(new_state & SCSI::Line::Busy) || time_since_change < SCSI::DeskewDelay) return;
+			state_ = ExecutionState::WatchingBusy;
+
+		case ExecutionState::WatchingBusy:
+			if(!(new_state & SCSI::Line::Busy)) {
+				lost_arbitration_ = true;
+				set_execution_state(ExecutionState::None);
+			}
+
+			// Check for having hit 400ns (more or less) since BSY was inactive.
+			if(time_since_change >= SCSI::BusSettleDelay) {
+//				arbitration_in_progress_ = false;
+				if(new_state & SCSI::Line::SelectTarget) {
+					lost_arbitration_ = true;
+					set_execution_state(ExecutionState::None);
+				} else {
+					bus_output_ &= ~SCSI::Line::Busy;
+					set_execution_state(ExecutionState::None);
+				}
+			}
+
+			/* TODO: there's a bug here, given that the dropping of Busy isn't communicated onward. */
+		break;
+
+		case ExecutionState::PerformingDMA:
+			if(time_since_change < SCSI::DeskewDelay) return;
+
+			// Signal a DMA request if the request line is active, i.e. meaningful data is
+			// on the bus, and this device hasn't yet acknowledged it.
+			switch(new_state & (SCSI::Line::Request | SCSI::Line::Acknowledge)) {
+				case 0:
+					dma_request_ = false;
+				break;
+				case SCSI::Line::Request:
+					dma_request_ = true;
+				break;
+				case SCSI::Line::Request | SCSI::Line::Acknowledge:
+					dma_request_ = false;
+				break;
+				case SCSI::Line::Acknowledge:
+					dma_acknowledge_ = false;
+					dma_request_ = false;
+					update_control_output();
+					bus_.set_device_output(device_id_, bus_output_);
+				break;
+			}
+		break;
+	}
+}
+
+void NCR5380::set_execution_state(ExecutionState state) {
+	state_ = state;
+	if(state != ExecutionState::PerformingDMA) dma_operation_ = DMAOperation::Ready;
+}

Components/5380/ncr5380.hpp

@@ -0,0 +1,75 @@
+//
+//  ncr5380.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 10/08/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef ncr5380_hpp
+#define ncr5380_hpp
+
+#include <cstdint>
+
+#include "../../Storage/MassStorage/SCSI/SCSI.hpp"
+
+
+namespace NCR {
+namespace NCR5380 {
+
+/*!
+	Models the NCR 5380, a SCSI interface chip.
+*/
+class NCR5380 final: public SCSI::Bus::Observer {
+	public:
+		NCR5380(SCSI::Bus &bus, int clock_rate);
+
+		/*! Writes @c value to @c address.  */
+		void write(int address, uint8_t value, bool dma_acknowledge = false);
+
+		/*! Reads from @c address. */
+		uint8_t read(int address, bool dma_acknowledge = false);
+
+	private:
+		SCSI::Bus &bus_;
+
+		const int clock_rate_;
+		size_t device_id_;
+
+		SCSI::BusState bus_output_ = SCSI::DefaultBusState;
+		SCSI::BusState expected_phase_ = SCSI::DefaultBusState;
+		uint8_t mode_ = 0xff;
+		uint8_t initiator_command_ = 0xff;
+		uint8_t data_bus_ = 0xff;
+		uint8_t target_command_ = 0xff;
+		bool test_mode_ = false;
+		bool assert_data_bus_ = false;
+		bool dma_request_ = false;
+		bool dma_acknowledge_ = false;
+
+		enum class ExecutionState {
+			None,
+			WaitingForBusy,
+			WatchingBusy,
+			PerformingDMA,
+		} state_ = ExecutionState::None;
+		enum class DMAOperation {
+			Ready,
+			Send,
+			TargetReceive,
+			InitiatorReceive
+		} dma_operation_ = DMAOperation::Ready;
+		bool lost_arbitration_ = false, arbitration_in_progress_ = false;
+
+		void set_execution_state(ExecutionState state);
+
+		SCSI::BusState target_output();
+		void update_control_output();
+
+		void scsi_bus_did_change(SCSI::Bus *, SCSI::BusState new_state, double time_since_change) final;
+};
+
+}
+}
+
+#endif /* ncr5380_hpp */

Components/6522/6522.hpp

@@ -47,6 +47,12 @@ class PortHandler {
 
 		/// Sets the current logical value of the interrupt line.
 		void set_interrupt_status(bool status)									{}
+
+		/// Provides a measure of time elapsed between other calls.
+		void run_for(HalfCycles duration)										{}
+
+		/// Receives passed-on flush() calls from the 6522.
+		void flush()															{}
 };
 
 /*!
@@ -71,8 +77,31 @@ class IRQDelegatePortHandler: public PortHandler {
 		Delegate *delegate_ = nullptr;
 };
 
-class MOS6522Base: public MOS6522Storage {
+/*!
+	Implements a template for emulation of the MOS 6522 Versatile Interface Adaptor ('VIA').
+
+	The VIA provides:
+		* two timers, each of which may trigger interrupts and one of which may repeat;
+		* two digial input/output ports; and
+		* a serial-to-parallel shifter.
+
+	Consumers should derive their own curiously-recurring-template-pattern subclass,
+	implementing bus communications as required.
+*/
+template <class T> class MOS6522: public MOS6522Storage {
 	public:
+		MOS6522(T &bus_handler) noexcept : bus_handler_(bus_handler) {}
+		MOS6522(const MOS6522 &) = delete;
+
+		/*! Sets a register value. */
+		void write(int address, uint8_t value);
+
+		/*! Gets a register value. */
+		uint8_t read(int address);
+
+		/*! @returns the bus handler. */
+		T &bus_handler();
+
 		/// Sets the input value of line @c line on port @c port.
 		void set_control_line_input(Port port, Line line, bool value);
 
@@ -85,47 +114,32 @@ class MOS6522Base: public MOS6522Storage {
 		/// @returns @c true if the IRQ line is currently active; @c false otherwise.
 		bool get_interrupt_line();
 
-	private:
-		inline void do_phase1();
-		inline void do_phase2();
-		virtual void reevaluate_interrupts() = 0;
-};
-
-/*!
-	Implements a template for emulation of the MOS 6522 Versatile Interface Adaptor ('VIA').
-
-	The VIA provides:
-		* two timers, each of which may trigger interrupts and one of which may repeat;
-		* two digial input/output ports; and
-		* a serial-to-parallel shifter.
-
-	Consumers should derive their own curiously-recurring-template-pattern subclass,
-	implementing bus communications as required.
-*/
-template <class T> class MOS6522: public MOS6522Base {
-	public:
-		MOS6522(T &bus_handler) noexcept : bus_handler_(bus_handler) {}
-		MOS6522(const MOS6522 &) = delete;
-
-		/*! Sets a register value. */
-		void set_register(int address, uint8_t value);
-
-		/*! Gets a register value. */
-		uint8_t get_register(int address);
-
-		/*! @returns the bus handler. */
-		T &bus_handler();
+		/// Updates the port handler to the current time and then requests that it flush.
+		void flush();
 
 	private:
+		void do_phase1();
+		void do_phase2();
+		void shift_in();
+		void shift_out();
+
 		T &bus_handler_;
+		HalfCycles time_since_bus_handler_call_;
+
+		void access(int address);
 
 		uint8_t get_port_input(Port port, uint8_t output_mask, uint8_t output);
 		inline void reevaluate_interrupts();
+
+		/// Sets the current intended output value for the port and line;
+		/// if this affects the visible output, it will be passed to the handler.
+		void set_control_line_output(Port port, Line line, LineState value);
+		void evaluate_cb2_output();
 };
 
+}
+}
+
 #include "Implementation/6522Implementation.hpp"
 
-}
-}
-
 #endif /* _522_hpp */

Components/6522/Implementation/6522Base.cpp

@@ -1,116 +0,0 @@
-//
-//  6522Base.cpp
-//  Clock Signal
-//
-//  Created by Thomas Harte on 04/09/2017.
-//  Copyright 2017 Thomas Harte. All rights reserved.
-//
-
-#include "../6522.hpp"
-
-using namespace MOS::MOS6522;
-
-void MOS6522Base::set_control_line_input(Port port, Line line, bool value) {
-	switch(line) {
-		case Line::One:
-			if(	value != control_inputs_[port].line_one &&
-				value == !!(registers_.peripheral_control & (port ? 0x10 : 0x01))
-			) {
-				registers_.interrupt_flags |= port ? InterruptFlag::CB1ActiveEdge : InterruptFlag::CA1ActiveEdge;
-				reevaluate_interrupts();
-			}
-			control_inputs_[port].line_one = value;
-		break;
-
-		case Line::Two:
-			// TODO: output modes, but probably elsewhere?
-			if(	value != control_inputs_[port].line_two &&							// i.e. value has changed ...
-				!(registers_.peripheral_control & (port ? 0x80 : 0x08)) &&			// ... and line is input ...
-				value == !!(registers_.peripheral_control & (port ? 0x40 : 0x04))	// ... and it's either high or low, as required
-			) {
-				registers_.interrupt_flags |= port ? InterruptFlag::CB2ActiveEdge : InterruptFlag::CA2ActiveEdge;
-				reevaluate_interrupts();
-			}
-			control_inputs_[port].line_two = value;
-		break;
-	}
-}
-
-void MOS6522Base::do_phase2() {
-	registers_.last_timer[0] = registers_.timer[0];
-	registers_.last_timer[1] = registers_.timer[1];
-
-	if(registers_.timer_needs_reload) {
-		registers_.timer_needs_reload = false;
-		registers_.timer[0] = registers_.timer_latch[0];
-	} else {
-		registers_.timer[0] --;
-	}
-
-	registers_.timer[1] --;
-	if(registers_.next_timer[0] >= 0) {
-		registers_.timer[0] = static_cast<uint16_t>(registers_.next_timer[0]);
-		registers_.next_timer[0] = -1;
-	}
-	if(registers_.next_timer[1] >= 0) {
-		registers_.timer[1] = static_cast<uint16_t>(registers_.next_timer[1]);
-		registers_.next_timer[1] = -1;
-	}
-}
-
-void MOS6522Base::do_phase1() {
-	// IRQ is raised on the half cycle after overflow
-	if((registers_.timer[1] == 0xffff) && !registers_.last_timer[1] && timer_is_running_[1]) {
-		timer_is_running_[1] = false;
-		registers_.interrupt_flags |= InterruptFlag::Timer2;
-		reevaluate_interrupts();
-	}
-
-	if((registers_.timer[0] == 0xffff) && !registers_.last_timer[0] && timer_is_running_[0]) {
-		registers_.interrupt_flags |= InterruptFlag::Timer1;
-		reevaluate_interrupts();
-
-		if(registers_.auxiliary_control&0x40)
-			registers_.timer_needs_reload = true;
-		else
-			timer_is_running_[0] = false;
-	}
-}
-
-/*! Runs for a specified number of half cycles. */
-void MOS6522Base::run_for(const HalfCycles half_cycles) {
-	int number_of_half_cycles = half_cycles.as_int();
-
-	if(is_phase2_) {
-		do_phase2();
-		number_of_half_cycles--;
-	}
-
-	while(number_of_half_cycles >= 2) {
-		do_phase1();
-		do_phase2();
-		number_of_half_cycles -= 2;
-	}
-
-	if(number_of_half_cycles) {
-		do_phase1();
-		is_phase2_ = true;
-	} else {
-		is_phase2_ = false;
-	}
-}
-
-/*! Runs for a specified number of cycles. */
-void MOS6522Base::run_for(const Cycles cycles) {
-	int number_of_cycles = cycles.as_int();
-	while(number_of_cycles--) {
-		do_phase1();
-		do_phase2();
-	}
-}
-
-/*! @returns @c true if the IRQ line is currently active; @c false otherwise. */
-bool MOS6522Base::get_interrupt_line() {
-	uint8_t interrupt_status = registers_.interrupt_flags & registers_.interrupt_enable & 0x7f;
-	return !!interrupt_status;
-}

Components/6522/Implementation/6522Implementation.hpp

@@ -6,29 +6,63 @@
 //  Copyright 2017 Thomas Harte. All rights reserved.
 //
 
-template <typename T> void MOS6522<T>::set_register(int address, uint8_t value) {
-	address &= 0xf;
+#include "../../../Outputs/Log.hpp"
+
+namespace MOS {
+namespace MOS6522 {
+
+template <typename T> void MOS6522<T>::access(int address) {
 	switch(address) {
 		case 0x0:
+			// In both handshake and pulse modes, CB2 goes low on any read or write of Port B.
+			if(handshake_modes_[1] != HandshakeMode::None) {
+				set_control_line_output(Port::B, Line::Two, LineState::Off);
+			}
+		break;
+
+		case 0xf:
+		case 0x1:
+			// In both handshake and pulse modes, CA2 goes low on any read or write of Port A.
+			if(handshake_modes_[0] != HandshakeMode::None) {
+				set_control_line_output(Port::A, Line::Two, LineState::Off);
+			}
+		break;
+	}
+}
+
+template <typename T> void MOS6522<T>::write(int address, uint8_t value) {
+	address &= 0xf;
+	access(address);
+	switch(address) {
+		case 0x0:	// Write Port B.
+			// Store locally and communicate outwards.
 			registers_.output[1] = value;
-			bus_handler_.set_port_output(Port::B, value, registers_.data_direction[1]);	// TODO: handshake
+
+			bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
+			bus_handler_.set_port_output(Port::B, value, registers_.data_direction[1]);
 
 			registers_.interrupt_flags &= ~(InterruptFlag::CB1ActiveEdge | ((registers_.peripheral_control&0x20) ? 0 : InterruptFlag::CB2ActiveEdge));
 			reevaluate_interrupts();
 		break;
 		case 0xf:
-		case 0x1:
+		case 0x1:	// Write Port A.
 			registers_.output[0] = value;
-			bus_handler_.set_port_output(Port::A, value, registers_.data_direction[0]);	// TODO: handshake
+
+			bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
+			bus_handler_.set_port_output(Port::A, value, registers_.data_direction[0]);
+
+			if(handshake_modes_[1] != HandshakeMode::None) {
+				set_control_line_output(Port::A, Line::Two, LineState::Off);
+			}
 
 			registers_.interrupt_flags &= ~(InterruptFlag::CA1ActiveEdge | ((registers_.peripheral_control&0x02) ? 0 : InterruptFlag::CB2ActiveEdge));
 			reevaluate_interrupts();
 		break;
 
-		case 0x2:
+		case 0x2:	// Port B direction.
 			registers_.data_direction[1] = value;
 		break;
-		case 0x3:
+		case 0x3:	// Port A direction.
 			registers_.data_direction[0] = value;
 		break;
 
@@ -54,32 +88,57 @@ template <typename T> void MOS6522<T>::set_register(int address, uint8_t value)
 		break;
 
 		// Shift
-		case 0xa:	registers_.shift = value;				break;
+		case 0xa:
+			registers_.shift = value;
+			shift_bits_remaining_ = 8;
+			registers_.interrupt_flags &= ~InterruptFlag::ShiftRegister;
+			reevaluate_interrupts();
+		break;
 
 		// Control
 		case 0xb:
 			registers_.auxiliary_control = value;
+			evaluate_cb2_output();
 		break;
-		case 0xc:
-//			printf("Peripheral control %02x\n", value);
+		case 0xc: {
+//			const auto old_peripheral_control = registers_.peripheral_control;
 			registers_.peripheral_control = value;
 
-			// TODO: simplify below; trying to avoid improper logging of unimplemented warnings in input mode
-			if(value & 0x08) {
-				switch(value & 0x0e) {
-					default: printf("Unimplemented control line mode %d\n", (value >> 1)&7);		break;
-					case 0x0c:	bus_handler_.set_control_line_output(Port::A, Line::Two, false);	break;
-					case 0x0e:	bus_handler_.set_control_line_output(Port::A, Line::Two, true);		break;
+			int shift = 0;
+			for(int port = 0; port < 2; ++port) {
+				handshake_modes_[port] = HandshakeMode::None;
+				switch((value >> shift) & 0x0e) {
+					default: break;
+
+					case 0x00:	// Negative interrupt input; set Cx2 interrupt on negative Cx2 transition, clear on access to Port x register.
+					case 0x02:	// Independent negative interrupt input; set Cx2 interrupt on negative transition, don't clear automatically.
+					case 0x04:	// Positive interrupt input; set Cx2 interrupt on positive Cx2 transition, clear on access to Port x register.
+					case 0x06:	// Independent positive interrupt input; set Cx2 interrupt on positive transition, don't clear automatically.
+						set_control_line_output(Port(port), Line::Two, LineState::Input);
+					break;
+
+					case 0x08:	// Handshake: set Cx2 to low on any read or write of Port x; set to high on an active transition of Cx1.
+						handshake_modes_[port] = HandshakeMode::Handshake;
+						set_control_line_output(Port(port), Line::Two, LineState::Off);	// At a guess.
+					break;
+
+					case 0x0a:	// Pulse output: Cx2 is low for one cycle following a read or write of Port x.
+						handshake_modes_[port] = HandshakeMode::Pulse;
+						set_control_line_output(Port(port), Line::Two, LineState::On);
+					break;
+
+					case 0x0c:	// Manual output: Cx2 low.
+						set_control_line_output(Port(port), Line::Two, LineState::Off);
+					break;
+
+					case 0x0e:	// Manual output: Cx2 high.
+						set_control_line_output(Port(port), Line::Two, LineState::On);
+					break;
 				}
+
+				shift += 4;
 			}
-			if(value & 0x80) {
-				switch(value & 0xe0) {
-					default: printf("Unimplemented control line mode %d\n", (value >> 5)&7);		break;
-					case 0xc0:	bus_handler_.set_control_line_output(Port::B, Line::Two, false);	break;
-					case 0xe0:	bus_handler_.set_control_line_output(Port::B, Line::Two, true);		break;
-				}
-			}
-		break;
+		} break;
 
 		// Interrupt control
 		case 0xd:
@@ -96,14 +155,15 @@ template <typename T> void MOS6522<T>::set_register(int address, uint8_t value)
 	}
 }
 
-template <typename T> uint8_t MOS6522<T>::get_register(int address) {
+template <typename T> uint8_t MOS6522<T>::read(int address) {
 	address &= 0xf;
+	access(address);
 	switch(address) {
 		case 0x0:
 			registers_.interrupt_flags &= ~(InterruptFlag::CB1ActiveEdge | InterruptFlag::CB2ActiveEdge);
 			reevaluate_interrupts();
 		return get_port_input(Port::B, registers_.data_direction[1], registers_.output[1]);
-		case 0xf:	// TODO: handshake, latching
+		case 0xf:
 		case 0x1:
 			registers_.interrupt_flags &= ~(InterruptFlag::CA1ActiveEdge | InterruptFlag::CA2ActiveEdge);
 			reevaluate_interrupts();
@@ -128,7 +188,11 @@ template <typename T> uint8_t MOS6522<T>::get_register(int address) {
 		return registers_.timer[1] & 0x00ff;
 		case 0x9:	return registers_.timer[1] >> 8;
 
-		case 0xa:	return registers_.shift;
+		case 0xa:
+			shift_bits_remaining_ = 8;
+			registers_.interrupt_flags &= ~InterruptFlag::ShiftRegister;
+			reevaluate_interrupts();
+		return registers_.shift;
 
 		case 0xb:	return registers_.auxiliary_control;
 		case 0xc:	return registers_.peripheral_control;
@@ -141,7 +205,8 @@ template <typename T> uint8_t MOS6522<T>::get_register(int address) {
 }
 
 template <typename T> uint8_t MOS6522<T>::get_port_input(Port port, uint8_t output_mask, uint8_t output) {
-	uint8_t input = bus_handler_.get_port_input(port);
+	bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
+	const uint8_t input = bus_handler_.get_port_input(port);
 	return (input & ~output_mask) | (output & output_mask);
 }
 
@@ -154,6 +219,238 @@ template <typename T> void MOS6522<T>::reevaluate_interrupts() {
 	bool new_interrupt_status = get_interrupt_line();
 	if(new_interrupt_status != last_posted_interrupt_status_) {
 		last_posted_interrupt_status_ = new_interrupt_status;
+
+		bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
 		bus_handler_.set_interrupt_status(new_interrupt_status);
 	}
 }
+
+template <typename T> void MOS6522<T>::set_control_line_input(Port port, Line line, bool value) {
+	switch(line) {
+		case Line::One:
+			if(value != control_inputs_[port].lines[line]) {
+				// In handshake mode, any transition on C[A/B]1 sets output high on C[A/B]2.
+				if(handshake_modes_[port] == HandshakeMode::Handshake) {
+					set_control_line_output(port, Line::Two, LineState::On);
+				}
+
+				// Set the proper transition interrupt bit if enabled.
+				if(value == !!(registers_.peripheral_control & (port ? 0x10 : 0x01))) {
+					registers_.interrupt_flags |= port ? InterruptFlag::CB1ActiveEdge : InterruptFlag::CA1ActiveEdge;
+					reevaluate_interrupts();
+				}
+
+				// If this is a transition on CB1, consider updating the shift register.
+				// TODO: and at least one full clock since the shift register was written?
+				if(port == Port::B) {
+					switch(shift_mode()) {
+						default: 													break;
+						case ShiftMode::InUnderCB1:		if(value)	shift_in();		break;	// Shifts in are captured on a low-to-high transition.
+						case ShiftMode::OutUnderCB1:	if(!value)	shift_out();	break;	// Shifts out are updated on a high-to-low transition.
+					}
+				}
+			}
+			control_inputs_[port].lines[line] = value;
+		break;
+
+		case Line::Two:
+			if(	value != control_inputs_[port].lines[line] &&						// i.e. value has changed ...
+				!(registers_.peripheral_control & (port ? 0x80 : 0x08)) &&			// ... and line is input ...
+				value == !!(registers_.peripheral_control & (port ? 0x40 : 0x04))	// ... and it's either high or low, as required
+			) {
+				registers_.interrupt_flags |= port ? InterruptFlag::CB2ActiveEdge : InterruptFlag::CA2ActiveEdge;
+				reevaluate_interrupts();
+			}
+			control_inputs_[port].lines[line] = value;
+		break;
+	}
+}
+
+template <typename T> void MOS6522<T>::do_phase2() {
+	++ time_since_bus_handler_call_;
+
+	registers_.last_timer[0] = registers_.timer[0];
+	registers_.last_timer[1] = registers_.timer[1];
+
+	if(registers_.timer_needs_reload) {
+		registers_.timer_needs_reload = false;
+		registers_.timer[0] = registers_.timer_latch[0];
+	} else {
+		registers_.timer[0] --;
+	}
+
+	registers_.timer[1] --;
+	if(registers_.next_timer[0] >= 0) {
+		registers_.timer[0] = static_cast<uint16_t>(registers_.next_timer[0]);
+		registers_.next_timer[0] = -1;
+	}
+	if(registers_.next_timer[1] >= 0) {
+		registers_.timer[1] = static_cast<uint16_t>(registers_.next_timer[1]);
+		registers_.next_timer[1] = -1;
+	}
+
+	// In pulse modes, CA2 and CB2 go high again on the next clock edge.
+	if(handshake_modes_[1] == HandshakeMode::Pulse) {
+		set_control_line_output(Port::B, Line::Two, LineState::On);
+	}
+	if(handshake_modes_[0] == HandshakeMode::Pulse) {
+		set_control_line_output(Port::A, Line::Two, LineState::On);
+	}
+
+	// If the shift register is shifting according to the input clock, do a shift.
+	switch(shift_mode()) {
+		default: 											break;
+		case ShiftMode::InUnderPhase2:		shift_in();		break;
+		case ShiftMode::OutUnderPhase2:		shift_out();	break;
+	}
+}
+
+template <typename T> void MOS6522<T>::do_phase1() {
+	++ time_since_bus_handler_call_;
+
+	// IRQ is raised on the half cycle after overflow
+	if((registers_.timer[1] == 0xffff) && !registers_.last_timer[1] && timer_is_running_[1]) {
+		timer_is_running_[1] = false;
+
+		// If the shift register is shifting according to this timer, do a shift.
+		// TODO: "shift register is driven by only the low order 8 bits of timer 2"?
+		switch(shift_mode()) {
+			default: 												break;
+			case ShiftMode::InUnderT2:				shift_in();		break;
+			case ShiftMode::OutUnderT2FreeRunning: 	shift_out();	break;
+			case ShiftMode::OutUnderT2:				shift_out();	break;	// TODO: present a clock on CB1.
+		}
+
+		registers_.interrupt_flags |= InterruptFlag::Timer2;
+		reevaluate_interrupts();
+	}
+
+	if((registers_.timer[0] == 0xffff) && !registers_.last_timer[0] && timer_is_running_[0]) {
+		registers_.interrupt_flags |= InterruptFlag::Timer1;
+		reevaluate_interrupts();
+
+		// Determine whether to reload.
+		if(registers_.auxiliary_control&0x40)
+			registers_.timer_needs_reload = true;
+		else
+			timer_is_running_[0] = false;
+
+		// Determine whether to toggle PB7.
+		if(registers_.auxiliary_control&0x80) {
+			registers_.output[1] ^= 0x80;
+			bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
+			bus_handler_.set_port_output(Port::B, registers_.output[1], registers_.data_direction[1]);
+		}
+	}
+}
+
+/*! Runs for a specified number of half cycles. */
+template <typename T> void MOS6522<T>::run_for(const HalfCycles half_cycles) {
+	auto number_of_half_cycles = half_cycles.as_integral();
+	if(!number_of_half_cycles) return;
+
+	if(is_phase2_) {
+		do_phase2();
+		number_of_half_cycles--;
+	}
+
+	while(number_of_half_cycles >= 2) {
+		do_phase1();
+		do_phase2();
+		number_of_half_cycles -= 2;
+	}
+
+	if(number_of_half_cycles) {
+		do_phase1();
+		is_phase2_ = true;
+	} else {
+		is_phase2_ = false;
+	}
+}
+
+template <typename T> void MOS6522<T>::flush() {
+	bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
+	bus_handler_.flush();
+}
+
+/*! Runs for a specified number of cycles. */
+template <typename T> void MOS6522<T>::run_for(const Cycles cycles) {
+	auto number_of_cycles = cycles.as_integral();
+	while(number_of_cycles--) {
+		do_phase1();
+		do_phase2();
+	}
+}
+
+/*! @returns @c true if the IRQ line is currently active; @c false otherwise. */
+template <typename T> bool MOS6522<T>::get_interrupt_line() {
+	uint8_t interrupt_status = registers_.interrupt_flags & registers_.interrupt_enable & 0x7f;
+	return !!interrupt_status;
+}
+
+template <typename T> void MOS6522<T>::evaluate_cb2_output() {
+	// CB2 is a special case, being both the line the shift register can output to,
+	// and one that can be used as an input or handshaking output according to the
+	// peripheral control register.
+
+	// My guess: other CB2 functions work only if the shift register is disabled (?).
+	if(shift_mode() != ShiftMode::Disabled) {
+		// Shift register is enabled, one way or the other; but announce only output.
+		if(is_shifting_out()) {
+			// Output mode; set the level according to the current top of the shift register.
+			bus_handler_.set_control_line_output(Port::B, Line::Two, !!(registers_.shift & 0x80));
+		} else {
+			// Input mode.
+			bus_handler_.set_control_line_output(Port::B, Line::Two, true);
+		}
+	} else {
+		// Shift register is disabled.
+		bus_handler_.set_control_line_output(Port::B, Line::Two, control_outputs_[1].lines[1] != LineState::Off);
+	}
+}
+
+template <typename T> void MOS6522<T>::set_control_line_output(Port port, Line line, LineState value) {
+	if(port == Port::B && line == Line::Two) {
+		control_outputs_[port].lines[line] = value;
+		evaluate_cb2_output();
+	} else {
+		// Do nothing if unchanged.
+		if(value == control_outputs_[port].lines[line]) {
+			return;
+		}
+
+		control_outputs_[port].lines[line] = value;
+
+		if(value != LineState::Input) {
+			bus_handler_.run_for(time_since_bus_handler_call_.flush<HalfCycles>());
+			bus_handler_.set_control_line_output(port, line, value != LineState::Off);
+		}
+	}
+}
+
+template <typename T> void MOS6522<T>::shift_in() {
+	registers_.shift = uint8_t((registers_.shift << 1) | (control_inputs_[1].lines[1] ? 1 : 0));
+	--shift_bits_remaining_;
+	if(!shift_bits_remaining_) {
+		registers_.interrupt_flags |= InterruptFlag::ShiftRegister;
+		reevaluate_interrupts();
+	}
+}
+
+template <typename T> void MOS6522<T>::shift_out() {
+	// When shifting out, the shift register rotates rather than strictly shifts.
+	// TODO: is that true for all modes?
+	if(shift_mode() == ShiftMode::OutUnderT2FreeRunning || shift_bits_remaining_) {
+		registers_.shift = uint8_t((registers_.shift << 1) | (registers_.shift >> 7));
+		evaluate_cb2_output();
+
+		--shift_bits_remaining_;
+		if(!shift_bits_remaining_) {
+			registers_.interrupt_flags |= InterruptFlag::ShiftRegister;
+			reevaluate_interrupts();
+		}
+	}
+}
+
+}
+}

Components/6522/Implementation/6522Storage.hpp

@@ -21,7 +21,7 @@ class MOS6522Storage {
 
 		// The registers
 		struct Registers {
-			// "A  low  reset  (RES)  input  clears  all  R6522  internal registers to logic 0"
+			// "A low reset (RES) input clears all R6522 internal registers to logic 0"
 			uint8_t output[2] = {0, 0};
 			uint8_t input[2] = {0, 0};
 			uint8_t data_direction[2] = {0, 0};
@@ -37,14 +37,27 @@ class MOS6522Storage {
 			bool timer_needs_reload = false;
 		} registers_;
 
-		// control state
+		// Control state.
 		struct {
-			bool line_one = false;
-			bool line_two = false;
+			bool lines[2] = {false, false};
 		} control_inputs_[2];
 
+		enum class LineState {
+			On, Off, Input
+		};
+		struct {
+			LineState lines[2] = {LineState::Input, LineState::Input};
+		} control_outputs_[2];
+
+		enum class HandshakeMode {
+			None,
+			Handshake,
+			Pulse
+		} handshake_modes_[2] = { HandshakeMode::None, HandshakeMode::None };
+
 		bool timer_is_running_[2] = {false, false};
 		bool last_posted_interrupt_status_ = false;
+		int shift_bits_remaining_ = 8;
 
 		enum InterruptFlag: uint8_t {
 			CA2ActiveEdge	= 1 << 0,
@@ -55,6 +68,23 @@ class MOS6522Storage {
 			Timer2			= 1 << 5,
 			Timer1			= 1 << 6,
 		};
+
+		enum class ShiftMode {
+			Disabled = 0,
+			InUnderT2 = 1,
+			InUnderPhase2 = 2,
+			InUnderCB1 = 3,
+			OutUnderT2FreeRunning = 4,
+			OutUnderT2 = 5,
+			OutUnderPhase2 = 6,
+			OutUnderCB1 = 7
+		};
+		ShiftMode shift_mode() const {
+			return ShiftMode((registers_.auxiliary_control >> 2) & 7);
+		}
+		bool is_shifting_out() const {
+			return registers_.auxiliary_control & 0x10;
+		}
 };
 
 }

Components/6532/6532.hpp

@@ -32,7 +32,7 @@ template <class T> class MOS6532 {
 		inline void set_ram(uint16_t address, uint8_t value)	{	ram_[address&0x7f] = value;		}
 		inline uint8_t get_ram(uint16_t address)				{	return ram_[address & 0x7f];	}
 
-		inline void set_register(int address, uint8_t value) {
+		inline void write(int address, uint8_t value) {
 			const uint8_t decodedAddress = address & 0x07;
 			switch(decodedAddress) {
 				// Port output
@@ -63,7 +63,7 @@ template <class T> class MOS6532 {
 			}
 		}
 
-		inline uint8_t get_register(int address) {
+		inline uint8_t read(int address) {
 			const uint8_t decodedAddress = address & 0x7;
 			switch(decodedAddress) {
 				// Port input
@@ -107,7 +107,7 @@ template <class T> class MOS6532 {
 		}
 
 		inline void run_for(const Cycles cycles) {
-			unsigned int number_of_cycles = static_cast<unsigned int>(cycles.as_int());
+			unsigned int number_of_cycles = static_cast<unsigned int>(cycles.as_integral());
 
 			// permit counting _to_ zero; counting _through_ zero initiates the other behaviour
 			if(timer_.value >= number_of_cycles) {

Components/6560/6560.hpp

@@ -34,7 +34,7 @@ class AudioGenerator: public ::Outputs::Speaker::SampleSource {
 	private:
 		Concurrency::DeferringAsyncTaskQueue &audio_queue_;
 
-		unsigned int counters_[4] = {2, 1, 0, 0}; 	// create a slight phase offset for the three channels
+		unsigned int counters_[4] = {2, 1, 0, 0};	// create a slight phase offset for the three channels
 		unsigned int shift_registers_[4] = {0, 0, 0, 0};
 		uint8_t control_registers_[4] = {0, 0, 0, 0};
 		int16_t volume_ = 0;
@@ -58,29 +58,18 @@ enum class OutputMode {
 	To run the VIC for a cycle, the caller should call @c get_address, make the requested bus access
 	and call @c set_graphics_value with the result.
 
-	@c set_register and @c get_register provide register access.
+	@c write and @c read provide register access.
 */
 template <class BusHandler> class MOS6560 {
 	public:
 		MOS6560(BusHandler &bus_handler) :
 				bus_handler_(bus_handler),
-				crt_(new Outputs::CRT::CRT(65*4, 4, Outputs::CRT::DisplayType::NTSC60, 2)),
+				crt_(65*4, 1, Outputs::Display::Type::NTSC60, Outputs::Display::InputDataType::Luminance8Phase8),
 				audio_generator_(audio_queue_),
 				speaker_(audio_generator_)
 		{
-			crt_->set_svideo_sampling_function(
-				"vec2 svideo_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
-				"{"
-					"vec2 yc = texture(texID, coordinate).rg / vec2(255.0);"
-
-					"float phaseOffset = 6.283185308 * 2.0 * yc.y;"
-					"float chroma = step(yc.y, 0.75) * cos(phase + phaseOffset);"
-
-					"return vec2(yc.x, chroma);"
-				"}");
-
 			// default to s-video output
-			crt_->set_video_signal(Outputs::CRT::VideoSignal::SVideo);
+			crt_.set_display_type(Outputs::Display::DisplayType::SVideo);
 
 			// default to NTSC
 			set_output_mode(OutputMode::NTSC);
@@ -94,7 +83,8 @@ template <class BusHandler> class MOS6560 {
 			speaker_.set_input_rate(static_cast<float>(clock_rate / 4.0));
 		}
 
-		Outputs::CRT::CRT *get_crt() { return crt_.get(); }
+		void set_scan_target(Outputs::Display::ScanTarget *scan_target)		{ crt_.set_scan_target(scan_target); 	}
+		void set_display_type(Outputs::Display::DisplayType display_type)	{ crt_.set_display_type(display_type); 	}
 		Outputs::Speaker::Speaker *get_speaker() { return &speaker_; }
 
 		void set_high_frequency_cutoff(float cutoff) {
@@ -117,12 +107,12 @@ template <class BusHandler> class MOS6560 {
 
 			// Chrominances are encoded such that 0-128 is a complete revolution of phase;
 			// anything above 191 disables the colour subcarrier. Phase is relative to the
-			// colour burst, so 0 is green.
+			// colour burst, so 0 is green (NTSC) or blue/violet (PAL).
 			const uint8_t pal_chrominances[16] = {
-				255,	255,	37,		101,
-				19,		86,		123,	59,
-				46,		53,		37,		101,
-				19,		86,		123,	59,
+				255,	255,	90,		20,
+				96,		42,		8,		72,
+				84,		90,		90,		20,
+				96,		42,		8,		72,
 			};
 			const uint8_t ntsc_chrominances[16] = {
 				255,	255,	121,	57,
@@ -131,12 +121,12 @@ template <class BusHandler> class MOS6560 {
 				103,	42,		80,		16,
 			};
 			const uint8_t *chrominances;
-			Outputs::CRT::DisplayType display_type;
+			Outputs::Display::Type display_type;
 
 			switch(output_mode) {
 				default:
 					chrominances = pal_chrominances;
-					display_type = Outputs::CRT::DisplayType::PAL50;
+					display_type = Outputs::Display::Type::PAL50;
 					timing_.cycles_per_line = 71;
 					timing_.line_counter_increment_offset = 4;
 					timing_.final_line_increment_position = timing_.cycles_per_line - timing_.line_counter_increment_offset;
@@ -146,7 +136,7 @@ template <class BusHandler> class MOS6560 {
 
 				case OutputMode::NTSC:
 					chrominances = ntsc_chrominances;
-					display_type = Outputs::CRT::DisplayType::NTSC60;
+					display_type = Outputs::Display::Type::NTSC60;
 					timing_.cycles_per_line = 65;
 					timing_.line_counter_increment_offset = 40;
 					timing_.final_line_increment_position = 58;
@@ -155,14 +145,14 @@ template <class BusHandler> class MOS6560 {
 				break;
 			}
 
-			crt_->set_new_display_type(static_cast<unsigned int>(timing_.cycles_per_line*4), display_type);
+			crt_.set_new_display_type(timing_.cycles_per_line*4, display_type);
 
 			switch(output_mode) {
 				case OutputMode::PAL:
-					crt_->set_visible_area(Outputs::CRT::Rect(0.1f, 0.07f, 0.9f, 0.9f));
+					crt_.set_visible_area(Outputs::Display::Rect(0.1f, 0.07f, 0.9f, 0.9f));
 				break;
 				case OutputMode::NTSC:
-					crt_->set_visible_area(Outputs::CRT::Rect(0.05f, 0.05f, 0.9f, 0.9f));
+					crt_.set_visible_area(Outputs::Display::Rect(0.05f, 0.05f, 0.9f, 0.9f));
 				break;
 			}
 
@@ -180,7 +170,7 @@ template <class BusHandler> class MOS6560 {
 			// keep track of the amount of time since the speaker was updated; lazy updates are applied
 			cycles_since_speaker_update_ += cycles;
 
-			int number_of_cycles = cycles.as_int();
+			auto number_of_cycles = cycles.as_integral();
 			while(number_of_cycles--) {
 				// keep an old copy of the vertical count because that test is a cycle later than the actual changes
 				int previous_vertical_counter = vertical_counter_;
@@ -284,17 +274,17 @@ template <class BusHandler> class MOS6560 {
 				// update the CRT
 				if(this_state_ != output_state_) {
 					switch(output_state_) {
-						case State::Sync:			crt_->output_sync(cycles_in_state_ * 4);														break;
-						case State::ColourBurst:	crt_->output_colour_burst(cycles_in_state_ * 4, (is_odd_frame_ || is_odd_line_) ? 128 : 0);		break;
-						case State::Border:			output_border(cycles_in_state_ * 4);															break;
-						case State::Pixels:			crt_->output_data(cycles_in_state_ * 4);														break;
+						case State::Sync:			crt_.output_sync(cycles_in_state_ * 4);														break;
+						case State::ColourBurst:	crt_.output_colour_burst(cycles_in_state_ * 4, (is_odd_frame_ || is_odd_line_) ? 128 : 0);	break;
+						case State::Border:			output_border(cycles_in_state_ * 4);														break;
+						case State::Pixels:			crt_.output_data(cycles_in_state_ * 4);														break;
 					}
 					output_state_ = this_state_;
 					cycles_in_state_ = 0;
 
 					pixel_pointer = nullptr;
 					if(output_state_ == State::Pixels) {
-						pixel_pointer = reinterpret_cast<uint16_t *>(crt_->allocate_write_area(260));
+						pixel_pointer = reinterpret_cast<uint16_t *>(crt_.begin_data(260));
 					}
 				}
 				cycles_in_state_++;
@@ -363,7 +353,7 @@ template <class BusHandler> class MOS6560 {
 		/*!
 			Writes to a 6560 register.
 		*/
-		void set_register(int address, uint8_t value) {
+		void write(int address, uint8_t value) {
 			address &= 0xf;
 			registers_.direct_values[address] = value;
 			switch(address) {
@@ -427,7 +417,7 @@ template <class BusHandler> class MOS6560 {
 		/*
 			Reads from a 6560 register.
 		*/
-		uint8_t get_register(int address) {
+		uint8_t read(int address) {
 			address &= 0xf;
 			switch(address) {
 				default: return registers_.direct_values[address];
@@ -438,7 +428,7 @@ template <class BusHandler> class MOS6560 {
 
 	private:
 		BusHandler &bus_handler_;
-		std::unique_ptr<Outputs::CRT::CRT> crt_;
+		Outputs::CRT::CRT crt_;
 
 		Concurrency::DeferringAsyncTaskQueue audio_queue_;
 		AudioGenerator audio_generator_;
@@ -451,12 +441,12 @@ template <class BusHandler> class MOS6560 {
 
 		// register state
 		struct {
-			bool interlaced, tall_characters;
+			bool interlaced = false, tall_characters = false;
 			uint8_t first_column_location, first_row_location;
 			uint8_t number_of_columns, number_of_rows;
 			uint16_t character_cell_start_address, video_matrix_start_address;
 			uint16_t backgroundColour, borderColour, auxiliary_colour;
-			bool invertedCells;
+			bool invertedCells = false;
 
 			uint8_t direct_values[16];
 		} registers_;
@@ -465,7 +455,7 @@ template <class BusHandler> class MOS6560 {
 		enum State {
 			Sync, ColourBurst, Border, Pixels
 		} this_state_, output_state_;
-		unsigned int cycles_in_state_;
+		int cycles_in_state_;
 
 		// counters that cover an entire field
 		int horizontal_counter_ = 0, vertical_counter_ = 0;
@@ -493,7 +483,7 @@ template <class BusHandler> class MOS6560 {
 		}
 
 		// latches dictating start and length of drawing
-		bool vertical_drawing_latch_, horizontal_drawing_latch_;
+		bool vertical_drawing_latch_ = false, horizontal_drawing_latch_ = false;
 		int rows_this_field_, columns_this_line_;
 
 		// current drawing position counter
@@ -511,10 +501,10 @@ template <class BusHandler> class MOS6560 {
 		uint16_t colours_[16];
 
 		uint16_t *pixel_pointer;
-		void output_border(unsigned int number_of_cycles) {
-			uint16_t *colour_pointer = reinterpret_cast<uint16_t *>(crt_->allocate_write_area(1));
+		void output_border(int number_of_cycles) {
+			uint16_t *colour_pointer = reinterpret_cast<uint16_t *>(crt_.begin_data(1));
 			if(colour_pointer) *colour_pointer = registers_.borderColour;
-			crt_->output_level(number_of_cycles);
+			crt_.output_level(number_of_cycles);
 		}
 
 		struct {

Components/6845/CRTC6845.hpp

@@ -111,7 +111,7 @@ template <class T> class CRTC6845 {
 		}
 
 		void run_for(Cycles cycles) {
-			int cyles_remaining = cycles.as_int();
+			auto cyles_remaining = cycles.as_integral();
 			while(cyles_remaining--) {
 				// check for end of visible characters
 				if(character_counter_ == registers_[1]) {

Components/6850/6850.cpp

@@ -0,0 +1,228 @@
+//
+//  6850.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 10/10/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "6850.hpp"
+
+#include <cassert>
+
+using namespace Motorola::ACIA;
+
+const HalfCycles ACIA::SameAsTransmit;
+
+ACIA::ACIA(HalfCycles transmit_clock_rate, HalfCycles receive_clock_rate) :
+	transmit_clock_rate_(transmit_clock_rate),
+	receive_clock_rate_((receive_clock_rate != SameAsTransmit) ? receive_clock_rate : transmit_clock_rate) {
+	transmit.set_writer_clock_rate(transmit_clock_rate);
+	request_to_send.set_writer_clock_rate(transmit_clock_rate);
+}
+
+uint8_t ACIA::read(int address) {
+	if(address&1) {
+		overran_ = false;
+		received_data_ |= NoValueMask;
+		update_interrupt_line();
+		return uint8_t(received_data_);
+	} else {
+		return get_status();
+	}
+}
+
+void ACIA::reset() {
+	transmit.reset_writing();
+	transmit.write(true);
+	request_to_send.reset_writing();
+
+	bits_received_ = bits_incoming_ = 0;
+	receive_interrupt_enabled_ = transmit_interrupt_enabled_ = false;
+	overran_ = false;
+	next_transmission_ = received_data_ = NoValueMask;
+
+	update_interrupt_line();
+	assert(!interrupt_line_);
+}
+
+void ACIA::write(int address, uint8_t value) {
+	if(address&1) {
+		next_transmission_ = value;
+		consider_transmission();
+		update_interrupt_line();
+	} else {
+		if((value&3) == 3) {
+			reset();
+		} else {
+			switch(value & 3) {
+				default:
+				case 0: divider_ = 1;	break;
+				case 1: divider_ = 16;	break;
+				case 2: divider_ = 64;	break;
+			}
+			switch((value >> 2) & 7) {
+				default:
+				case 0:	data_bits_ = 7; stop_bits_ = 2; parity_ = Parity::Even;	break;
+				case 1:	data_bits_ = 7; stop_bits_ = 2; parity_ = Parity::Odd;	break;
+				case 2:	data_bits_ = 7; stop_bits_ = 1; parity_ = Parity::Even;	break;
+				case 3:	data_bits_ = 7; stop_bits_ = 1; parity_ = Parity::Odd;	break;
+				case 4:	data_bits_ = 8; stop_bits_ = 2; parity_ = Parity::None;	break;
+				case 5:	data_bits_ = 8; stop_bits_ = 1; parity_ = Parity::None;	break;
+				case 6:	data_bits_ = 8; stop_bits_ = 1; parity_ = Parity::Even;	break;
+				case 7:	data_bits_ = 8; stop_bits_ = 1; parity_ = Parity::Odd;	break;
+			}
+			switch((value >> 5) & 3) {
+				case 0:	request_to_send.write(false); transmit_interrupt_enabled_ = false;	break;
+				case 1:	request_to_send.write(false); transmit_interrupt_enabled_ = true;	break;
+				case 2:	request_to_send.write(true); transmit_interrupt_enabled_ = false;	break;
+				case 3:
+					request_to_send.write(false);
+					transmit_interrupt_enabled_ = false;
+					transmit.reset_writing();
+					transmit.write(false);
+				break;
+			}
+			receive.set_read_delegate(this, Storage::Time(divider_ * 2, int(receive_clock_rate_.as_integral())));
+			receive_interrupt_enabled_ = value & 0x80;
+
+			update_interrupt_line();
+		}
+	}
+	update_clocking_observer();
+}
+
+void ACIA::consider_transmission() {
+	if(next_transmission_ != NoValueMask && !transmit.write_data_time_remaining()) {
+		// Establish start bit and [7 or 8] data bits.
+		if(data_bits_ == 7) next_transmission_ &= 0x7f;
+		int transmission = next_transmission_ << 1;
+
+		// Add a parity bit, if any.
+		int mask = 0x2 << data_bits_;
+		if(parity_ != Parity::None) {
+			transmission |= parity(uint8_t(next_transmission_)) ? mask : 0;
+			mask <<= 1;
+		}
+
+		// Add stop bits.
+		for(int c = 0; c < stop_bits_; ++c) {
+			transmission |= mask;
+			mask <<= 1;
+		}
+
+		// Output all that.
+		const int total_bits = expected_bits();
+		transmit.write(divider_ * 2, total_bits, transmission);
+
+		// Mark the transmit register as empty again.
+		next_transmission_ = NoValueMask;
+	}
+}
+
+ClockingHint::Preference ACIA::preferred_clocking() {
+	// Real-time clocking is required if a transmission is ongoing; this is a courtesy for whomever
+	// is on the receiving end.
+	if(transmit.transmission_data_time_remaining() > 0) return ClockingHint::Preference::RealTime;
+
+	// If a bit reception is ongoing that might lead to an interrupt, ask for real-time clocking
+	// because it's unclear when the interrupt might come.
+	if(bits_incoming_ && receive_interrupt_enabled_) return ClockingHint::Preference::RealTime;
+
+	// No clocking required then.
+	return ClockingHint::Preference::None;
+}
+
+bool ACIA::get_interrupt_line() const {
+	return interrupt_line_;
+}
+
+int ACIA::expected_bits() {
+	return 1 + data_bits_ + stop_bits_ + (parity_ != Parity::None);
+}
+
+uint8_t ACIA::parity(uint8_t value) {
+	value ^= value >> 4;
+	value ^= value >> 2;
+	value ^= value >> 1;
+	return value ^ (parity_ == Parity::Even);
+}
+
+bool ACIA::serial_line_did_produce_bit(Serial::Line *line, int bit) {
+	// Shift this bit into the 11-bit input register; this is big enough to hold
+	// the largest transmission symbol.
+	++bits_received_;
+	bits_incoming_ = (bits_incoming_ >> 1) | (bit << 10);
+
+	// If that's the now-expected number of bits, update.
+	const int bit_target = expected_bits();
+	if(bits_received_ >= bit_target) {
+		bits_received_ = 0;
+		overran_ |= get_status() & 1;
+		received_data_ = uint8_t(bits_incoming_ >> (12 - bit_target));
+		update_interrupt_line();
+		update_clocking_observer();
+		return false;
+	}
+
+	// TODO: overrun, and parity.
+
+	// Keep receiving, and consider a potential clocking change.
+	if(bits_received_ == 1) update_clocking_observer();
+	return true;
+}
+
+void ACIA::set_interrupt_delegate(InterruptDelegate *delegate) {
+	interrupt_delegate_ = delegate;
+}
+
+void ACIA::update_interrupt_line() {
+	const bool old_line = interrupt_line_;
+
+	/*
+		"Bit 7 of the control register is the rie bit. When the rie bit is high, the rdrf, ndcd,
+		and ovr bits will assert the nirq output. When the rie bit is low, nirq generation is disabled."
+
+		rie = read interrupt enable
+		rdrf = receive data register full (status word bit 0)
+		ndcd = data carrier detect (status word bit 2)
+		over = receiver overrun (status word bit 5)
+
+		"Bit 1 of the status register is the tdre bit. When high, the tdre bit indicates that data has been
+		transferred from the transmitter data register to the output shift register. At this point, the a6850
+		is ready to accept a new transmit data byte. However, if the ncts signal is high, the tdre bit remains
+		low regardless of the status of the transmitter data register. Also, if transmit interrupt is enabled,
+		the nirq output is asserted."
+
+		tdre = transmitter data register empty
+		ncts = clear to send
+	*/
+	const auto status = get_status();
+	interrupt_line_ =
+		(receive_interrupt_enabled_ && (status & 0x25)) ||
+		(transmit_interrupt_enabled_ && (status & 0x02));
+
+	if(interrupt_delegate_ && old_line != interrupt_line_) {
+		interrupt_delegate_->acia6850_did_change_interrupt_status(this);
+	}
+}
+
+uint8_t ACIA::get_status() {
+	return
+		((received_data_ & NoValueMask) ? 0x00 : 0x01) |
+		((next_transmission_ == NoValueMask) ? 0x02 : 0x00) |
+//		(data_carrier_detect.read() ? 0x04 : 0x00) |
+//		(clear_to_send.read() ? 0x08 : 0x00) |
+		(overran_ ? 0x20 : 0x00) |
+		(interrupt_line_ ? 0x80 : 0x00)
+	;
+
+	// b0: receive data full.
+	// b1: transmit data empty.
+	// b2: DCD.
+	// b3: CTS.
+	// b4: framing error (i.e. no first stop bit where expected).
+	// b5: receiver overran.
+	// b6: parity error.
+	// b7: IRQ state.
+}

Components/6850/6850.hpp

@@ -0,0 +1,132 @@
+//
+//  6850.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 10/10/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef Motorola_ACIA_6850_hpp
+#define Motorola_ACIA_6850_hpp
+
+#include <cstdint>
+#include "../../ClockReceiver/ClockReceiver.hpp"
+#include "../../ClockReceiver/ForceInline.hpp"
+#include "../../ClockReceiver/ClockingHintSource.hpp"
+#include "../Serial/Line.hpp"
+
+namespace Motorola {
+namespace ACIA {
+
+class ACIA: public ClockingHint::Source, private Serial::Line::ReadDelegate {
+	public:
+		static constexpr const HalfCycles SameAsTransmit = HalfCycles(0);
+
+		/*!
+			Constructs a new instance of ACIA which will receive a transmission clock at a rate of
+			@c transmit_clock_rate, and a receive clock at a rate of @c receive_clock_rate.
+		*/
+		ACIA(HalfCycles transmit_clock_rate, HalfCycles receive_clock_rate = SameAsTransmit);
+
+		/*!
+			Reads from the ACIA.
+
+			Bit 0 of the address is used as the ACIA's register select line —
+			so even addresses select control/status registers, odd addresses
+			select transmit/receive data registers.
+		*/
+		uint8_t read(int address);
+
+		/*!
+			Writes to the ACIA.
+
+			Bit 0 of the address is used as the ACIA's register select line —
+			so even addresses select control/status registers, odd addresses
+			select transmit/receive data registers.
+		*/
+		void write(int address, uint8_t value);
+
+		/*!
+			Advances @c transmission_cycles in time, which should be
+			counted relative to the @c transmit_clock_rate.
+		*/
+		forceinline void run_for(HalfCycles transmission_cycles) {
+			if(transmit.transmission_data_time_remaining() > HalfCycles(0)) {
+				const auto write_data_time_remaining = transmit.write_data_time_remaining();
+
+				// There's at most one further byte available to enqueue, so a single 'if'
+				// rather than a 'while' is correct here. It's the responsibilit of the caller
+				// to ensure run_for lengths are appropriate for longer sequences.
+				if(transmission_cycles >= write_data_time_remaining) {
+					if(next_transmission_ != NoValueMask) {
+						transmit.advance_writer(write_data_time_remaining);
+						consider_transmission();
+						transmit.advance_writer(transmission_cycles - write_data_time_remaining);
+					} else {
+						transmit.advance_writer(transmission_cycles);
+						update_clocking_observer();
+						update_interrupt_line();
+					}
+				} else {
+					transmit.advance_writer(transmission_cycles);
+				}
+			}
+		}
+
+		bool get_interrupt_line() const;
+		void reset();
+
+		// Input lines.
+		Serial::Line receive;
+		Serial::Line clear_to_send;
+		Serial::Line data_carrier_detect;
+
+		// Output lines.
+		Serial::Line transmit;
+		Serial::Line request_to_send;
+
+		// ClockingHint::Source.
+		ClockingHint::Preference preferred_clocking() final;
+
+		struct InterruptDelegate {
+			virtual void acia6850_did_change_interrupt_status(ACIA *acia) = 0;
+		};
+		void set_interrupt_delegate(InterruptDelegate *delegate);
+
+	private:
+		int divider_ = 1;
+		enum class Parity {
+			Even, Odd, None
+		} parity_ = Parity::None;
+		int data_bits_ = 7, stop_bits_ = 2;
+
+		static constexpr int NoValueMask = 0x100;
+		int next_transmission_ = NoValueMask;
+		int received_data_ = NoValueMask;
+
+		int bits_received_ = 0;
+		int bits_incoming_ = 0;
+		bool overran_ = false;
+
+		void consider_transmission();
+		int expected_bits();
+		uint8_t parity(uint8_t value);
+
+		bool receive_interrupt_enabled_ = false;
+		bool transmit_interrupt_enabled_ = false;
+
+		HalfCycles transmit_clock_rate_;
+		HalfCycles receive_clock_rate_;
+
+		bool serial_line_did_produce_bit(Serial::Line *line, int bit) final;
+
+		bool interrupt_line_ = false;
+		void update_interrupt_line();
+		InterruptDelegate *interrupt_delegate_ = nullptr;
+		uint8_t get_status();
+};
+
+}
+}
+
+#endif /* Motorola_ACIA_6850_hpp */

Components/68901/MFP68901.cpp

@@ -0,0 +1,374 @@
+//
+//  MFP68901.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 06/10/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "MFP68901.hpp"
+
+#include <algorithm>
+#include <cstring>
+
+#ifndef NDEBUG
+#define NDEBUG
+#endif
+
+#define LOG_PREFIX "[MFP] "
+#include "../../Outputs/Log.hpp"
+
+using namespace Motorola::MFP68901;
+
+ClockingHint::Preference MFP68901::preferred_clocking() {
+	// Rule applied: if any timer is actively running and permitted to produce an
+	// interrupt, request real-time running.
+	return
+		(timers_[0].mode >= TimerMode::Delay && interrupt_enable_&Interrupt::TimerA) ||
+		(timers_[1].mode >= TimerMode::Delay && interrupt_enable_&Interrupt::TimerB) ||
+		(timers_[2].mode >= TimerMode::Delay && interrupt_enable_&Interrupt::TimerC) ||
+		(timers_[3].mode >= TimerMode::Delay && interrupt_enable_&Interrupt::TimerD)
+			? ClockingHint::Preference::RealTime : ClockingHint::Preference::JustInTime;
+}
+
+uint8_t MFP68901::read(int address) {
+	address &= 0x1f;
+
+	// Interrupt block: various bits of state can be read, all passively.
+	if(address >= 0x03 && address <= 0x0b) {
+		const int shift = (address&1) << 3;
+		switch(address) {
+			case 0x03:	case 0x04:	return uint8_t(interrupt_enable_ >> shift);
+			case 0x05:	case 0x06:	return uint8_t(interrupt_pending_ >> shift);
+			case 0x07:	case 0x08:	return uint8_t(interrupt_in_service_ >> shift);
+			case 0x09:	case 0x0a:	return uint8_t(interrupt_mask_ >> shift);
+			case 0x0b:	return interrupt_vector_;
+
+			default: break;
+		}
+	}
+
+	switch(address) {
+		// GPIP block: input, and configured active edge and direction values.
+		case 0x00:	return (gpip_input_ & ~gpip_direction_) | (gpip_output_ & gpip_direction_);
+		case 0x01:	return gpip_active_edge_;
+		case 0x02:	return gpip_direction_;
+
+		/* Interrupt block dealt with above. */
+		default: break;
+
+		// Timer block: read back A, B and C/D control, and read current timer values.
+		case 0x0c:	case 0x0d:	return timer_ab_control_[address - 0xc];
+		case 0x0e:				return timer_cd_control_;
+		case 0x0f:	case 0x10:
+		case 0x11:	case 0x12:	return get_timer_data(address - 0xf);
+
+		// USART block: TODO.
+		case 0x13:		LOG("Read: sync character generator");	break;
+		case 0x14:		LOG("Read: USART control");				break;
+		case 0x15:		LOG("Read: receiver status");			break;
+		case 0x16:		LOG("Read: transmitter status");		break;
+		case 0x17:		LOG("Read: USART data");				break;
+	}
+	return 0x00;
+}
+
+void MFP68901::write(int address, uint8_t value) {
+	address &= 0x1f;
+
+	// Interrupt block: enabled and masked interrupts can be set; pending and in-service interrupts can be masked.
+	if(address >= 0x03 && address <= 0x0b) {
+		const int shift = (address&1) << 3;
+		const int preserve = 0xff00 >> shift;
+		const int word_value = value << shift;
+
+		switch(address) {
+			default: break;
+			case 0x03: case 0x04:	// Adjust enabled interrupts; disabled ones also cease to be pending.
+				interrupt_enable_ = (interrupt_enable_ & preserve) | word_value;
+				interrupt_pending_ &= interrupt_enable_;
+			break;
+			case 0x05: case 0x06:	// Resolve pending interrupts.
+				interrupt_pending_ &= (preserve | word_value);
+			break;
+			case 0x07: case 0x08:	// Resolve in-service interrupts.
+				interrupt_in_service_ &= (preserve | word_value);
+			break;
+			case 0x09: case 0x0a:	// Adjust interrupt mask.
+				interrupt_mask_ = (interrupt_mask_ & preserve) | word_value;
+			break;
+			case 0x0b:				// Set the interrupt vector, possibly changing end-of-interrupt mode.
+				interrupt_vector_ = value;
+
+				// If automatic end-of-interrupt mode has now been enabled, clear
+				// the in-process mask and re-evaluate.
+				if(interrupt_vector_ & 0x08) return;
+				interrupt_in_service_ = 0;
+			break;
+		}
+
+		// Whatever just happened may have affected the state of the interrupt line.
+		update_interrupts();
+		update_clocking_observer();
+		return;
+	}
+
+	constexpr int timer_prescales[] = {
+		1, 4, 10, 16, 50, 64, 100, 200
+	};
+
+	switch(address) {
+		// GPIP block: output and configuration of active edge and direction values.
+		case 0x00:
+			gpip_output_ = value;
+		break;
+		case 0x01:
+			gpip_active_edge_ = value;
+			reevaluate_gpip_interrupts();
+		break;
+		case 0x02:
+			gpip_direction_ = value;
+			reevaluate_gpip_interrupts();
+		break;
+
+		/* Interrupt block dealt with above. */
+		default: break;
+
+		// Timer block.
+		case 0x0c:
+		case 0x0d: {
+			const auto timer = address - 0xc;
+			const bool reset = value & 0x10;
+			timer_ab_control_[timer] = value;
+			switch(value & 0xf) {
+				case 0x0:	set_timer_mode(timer, TimerMode::Stopped, 1, reset);		break;
+				case 0x1:	set_timer_mode(timer, TimerMode::Delay, 4, reset);			break;
+				case 0x2:	set_timer_mode(timer, TimerMode::Delay, 10, reset);			break;
+				case 0x3:	set_timer_mode(timer, TimerMode::Delay, 16, reset);			break;
+				case 0x4:	set_timer_mode(timer, TimerMode::Delay, 50, reset);			break;
+				case 0x5:	set_timer_mode(timer, TimerMode::Delay, 64, reset);			break;
+				case 0x6:	set_timer_mode(timer, TimerMode::Delay, 100, reset);		break;
+				case 0x7:	set_timer_mode(timer, TimerMode::Delay, 200, reset);		break;
+				case 0x8:	set_timer_mode(timer, TimerMode::EventCount, 1, reset);		break;
+				case 0x9:	set_timer_mode(timer, TimerMode::PulseWidth, 4, reset);		break;
+				case 0xa:	set_timer_mode(timer, TimerMode::PulseWidth, 10, reset);	break;
+				case 0xb:	set_timer_mode(timer, TimerMode::PulseWidth, 16, reset);	break;
+				case 0xc:	set_timer_mode(timer, TimerMode::PulseWidth, 50, reset);	break;
+				case 0xd:	set_timer_mode(timer, TimerMode::PulseWidth, 64, reset);	break;
+				case 0xe:	set_timer_mode(timer, TimerMode::PulseWidth, 100, reset);	break;
+				case 0xf:	set_timer_mode(timer, TimerMode::PulseWidth, 200, reset);	break;
+			}
+		} break;
+		case 0x0e:
+			timer_cd_control_ = value;
+			set_timer_mode(3, (value & 7) ? TimerMode::Delay : TimerMode::Stopped, timer_prescales[value & 7], false);
+			set_timer_mode(2, ((value >> 4) & 7) ? TimerMode::Delay : TimerMode::Stopped, timer_prescales[(value >> 4) & 7], false);
+		break;
+		case 0x0f:	case 0x10:	case 0x11:	case 0x12:
+			set_timer_data(address - 0xf, value);
+		break;
+
+		// USART block: TODO.
+		case 0x13:		LOG("Write: sync character generator");	break;
+		case 0x14:		LOG("Write: USART control");			break;
+		case 0x15:		LOG("Write: receiver status");			break;
+		case 0x16:		LOG("Write: transmitter status");		break;
+		case 0x17:		LOG("Write: USART data");				break;
+	}
+
+	update_clocking_observer();
+}
+
+void MFP68901::run_for(HalfCycles time) {
+	cycles_left_ += time;
+
+	const int cycles = int(cycles_left_.flush<Cycles>().as_integral());
+	if(!cycles) return;
+
+	for(int c = 0; c < 4; ++c) {
+		if(timers_[c].mode >= TimerMode::Delay) {
+			// This code applies the timer prescaling only. prescale_count is used to count
+			// upwards rather than downwards for simplicity, but on the real hardware it's
+			// pretty safe to assume it actually counted downwards. So the clamp to 0 is
+			// because gymnastics may need to occur when the prescale value is altered, e.g.
+			// if a prescale of 256 is set and the prescale_count is currently 2 then the
+			// counter should roll over in 254 cycles. If the user at that point changes the
+			// prescale_count to 1 then the counter will need to be altered to -253 and
+			// allowed to keep counting up until it crosses both 0 and 1.
+			const int dividend = timers_[c].prescale_count + cycles;
+			const int decrements = std::max(dividend / timers_[c].prescale, 0);
+			if(decrements) {
+				decrement_timer(c, decrements);
+				timers_[c].prescale_count = dividend % timers_[c].prescale;
+			} else {
+				timers_[c].prescale_count += cycles;
+			}
+		}
+	}
+}
+
+HalfCycles MFP68901::get_next_sequence_point() {
+	return HalfCycles(-1);
+}
+
+// MARK: - Timers
+
+void MFP68901::set_timer_mode(int timer, TimerMode mode, int prescale, bool reset_timer) {
+	LOG("Timer " << timer << " mode set: " << int(mode) << "; prescale: " << prescale);
+	timers_[timer].mode = mode;
+	if(reset_timer) {
+		timers_[timer].prescale_count = 0;
+		timers_[timer].value = timers_[timer].reload_value;
+	} else {
+		// This hoop is because the prescale_count here goes upward but I'm assuming it goes downward in
+		// real hardware. Therefore this deals with the "switched to a lower prescaling" case whereby the
+		// old cycle should be allowed naturally to expire.
+		timers_[timer].prescale_count = prescale - (timers_[timer].prescale - timers_[timer].prescale_count);
+	}
+
+	timers_[timer].prescale = prescale;
+}
+
+void MFP68901::set_timer_data(int timer, uint8_t value) {
+	if(timers_[timer].mode == TimerMode::Stopped) {
+		timers_[timer].value = value;
+	}
+	timers_[timer].reload_value = value;
+}
+
+uint8_t MFP68901::get_timer_data(int timer) {
+	return timers_[timer].value;
+}
+
+void MFP68901::set_timer_event_input(int channel, bool value) {
+	if(timers_[channel].event_input == value) return;
+
+	timers_[channel].event_input = value;
+	if(timers_[channel].mode == TimerMode::EventCount && (value == !!(gpip_active_edge_ & (0x10 >> channel)))) {
+		// "The active state of the signal on TAI or TBI is dependent upon the associated
+		// Interrupt Channel’s edge bit (GPIP 4 for TAI and GPIP 3 for TBI [...] ).
+		// If the edge bit associated with the TAI or TBI input is a one, it will be active high.
+		decrement_timer(channel, 1);
+	}
+
+	// TODO:
+	//
+	// Altering the edge bit while the timer is in the event count mode can produce a count pulse.
+	// The interrupt channel associated with the input (I3 for I4 for TAI) is allowed to function normally.
+	// To count transitions reliably, the input must remain in each state (1/O) for a length of time equal
+	// to four periods of the timer clock.
+	//
+	// (the final bit probably explains 13 cycles of the DE to interrupt latency; not sure about the other ~15)
+}
+
+void MFP68901::decrement_timer(int timer, int amount) {
+	while(amount--) {
+		--timers_[timer].value;
+		if(timers_[timer].value < 1) {
+			switch(timer) {
+				case 0: begin_interrupts(Interrupt::TimerA);	break;
+				case 1: begin_interrupts(Interrupt::TimerB);	break;
+				case 2: begin_interrupts(Interrupt::TimerC);	break;
+				case 3: begin_interrupts(Interrupt::TimerD);	break;
+			}
+
+			// Re: reloading when in event counting mode; I found the data sheet thoroughly unclear on
+			// this, but it appears empirically to be correct. See e.g. Pompey Pirates menu 27.
+			if(timers_[timer].mode == TimerMode::Delay || timers_[timer].mode == TimerMode::EventCount) {
+				timers_[timer].value += timers_[timer].reload_value;	// TODO: properly.
+			}
+		}
+	}
+}
+
+// MARK: - GPIP
+void MFP68901::set_port_input(uint8_t input) {
+	gpip_input_ = input;
+	reevaluate_gpip_interrupts();
+}
+
+uint8_t MFP68901::get_port_output() {
+	return 0xff;	// TODO.
+}
+
+void MFP68901::reevaluate_gpip_interrupts() {
+	const uint8_t gpip_state = (gpip_input_ & ~gpip_direction_) ^ gpip_active_edge_;
+
+	// An interrupt is detected on any falling edge.
+	const uint8_t new_interrupt_mask = (gpip_state ^ gpip_interrupt_state_) & gpip_interrupt_state_;
+	if(new_interrupt_mask) {
+		begin_interrupts(
+			(new_interrupt_mask & 0x0f) |
+			((new_interrupt_mask & 0x30) << 2) |
+			((new_interrupt_mask & 0xc0) << 8)
+		);
+	}
+	gpip_interrupt_state_ = gpip_state;
+}
+
+// MARK: - Interrupts
+
+void MFP68901::begin_interrupts(int interrupt) {
+	interrupt_pending_ |= interrupt & interrupt_enable_;
+	update_interrupts();
+}
+
+void MFP68901::end_interrupts(int interrupt) {
+	interrupt_pending_ &= ~interrupt;
+	update_interrupts();
+}
+
+void MFP68901::update_interrupts() {
+	const auto old_interrupt_line = interrupt_line_;
+	const auto firing_interrupts = interrupt_pending_ & interrupt_mask_;
+
+	if(!firing_interrupts) {
+		interrupt_line_ = false;
+	} else {
+		if(interrupt_vector_ & 0x8) {
+			// Software interrupt mode: permit only if neither this interrupt
+			// nor a higher interrupt is currently in service.
+			const int highest_bit = msb16(firing_interrupts);
+			interrupt_line_ = !(interrupt_in_service_ & ~(highest_bit + highest_bit - 1));
+		} else {
+			// Auto-interrupt mode; just signal.
+			interrupt_line_ = true;
+		}
+	}
+
+	// Update the delegate if necessary.
+	if(interrupt_delegate_ && interrupt_line_ != old_interrupt_line) {
+		interrupt_delegate_->mfp68901_did_change_interrupt_status(this);
+	}
+}
+
+bool MFP68901::get_interrupt_line() {
+	return interrupt_line_;
+}
+
+int MFP68901::acknowledge_interrupt() {
+	if(!(interrupt_pending_ & interrupt_mask_)) {
+		return NoAcknowledgement;
+	}
+
+	const int mask = msb16(interrupt_pending_ & interrupt_mask_);
+
+	// Clear the pending bit regardless.
+	interrupt_pending_ &= ~mask;
+
+	// If this is software interrupt mode, set the in-service bit.
+	if(interrupt_vector_ & 0x8) {
+		interrupt_in_service_ |= mask;
+	}
+
+	update_interrupts();
+
+	int selected = 0;
+	while((1 << selected) != mask) ++selected;
+//	LOG("Interrupt acknowledged: " << selected);
+	return (interrupt_vector_ & 0xf0) | uint8_t(selected);
+}
+
+void MFP68901::set_interrupt_delegate(InterruptDelegate *delegate) {
+	interrupt_delegate_ = delegate;
+}

Components/68901/MFP68901.hpp

@@ -0,0 +1,187 @@
+//
+//  MFP68901.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 06/10/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef MFP68901_hpp
+#define MFP68901_hpp
+
+#include <cstdint>
+#include "../../ClockReceiver/ClockReceiver.hpp"
+#include "../../ClockReceiver/ClockingHintSource.hpp"
+
+namespace Motorola {
+namespace MFP68901 {
+
+class PortHandler {
+	public:
+		// TODO: announce changes in output.
+};
+
+/*!
+	Models the Motorola 68901 Multi-Function Peripheral ('MFP').
+*/
+class MFP68901: public ClockingHint::Source {
+	public:
+		/// @returns the result of a read from @c address.
+		uint8_t read(int address);
+
+		/// Performs a write of @c value to @c address.
+		void write(int address, uint8_t value);
+
+		/// Advances the MFP by the supplied number of HalfCycles.
+		void run_for(HalfCycles);
+
+		/// @returns the number of cycles until the next possible sequence point — the next time
+		/// at which the interrupt line _might_ change. This object conforms to ClockingHint::Source
+		/// so that mechanism can also be used to reduce the quantity of calls into this class.
+		///
+		/// @discussion TODO, alas.
+		HalfCycles get_next_sequence_point();
+
+		/// Sets the current level of either of the timer event inputs — TAI and TBI in datasheet terms.
+		void set_timer_event_input(int channel, bool value);
+
+		/// Sets a port handler, a receiver that will be notified upon any change in GPIP output.
+		///
+		/// @discussion TODO.
+		void set_port_handler(PortHandler *);
+
+		/// Sets the current input GPIP values.
+		void set_port_input(uint8_t);
+
+		/// @returns the current GPIP output values.
+		///
+		/// @discussion TODO.
+		uint8_t get_port_output();
+
+		/// @returns @c true if the interrupt output is currently active; @c false otherwise.s
+		bool get_interrupt_line();
+
+		static constexpr int NoAcknowledgement = 0x100;
+
+		/// Communicates an interrupt acknowledge cycle.
+		///
+		/// @returns the vector placed on the bus if any; @c NoAcknowledgement if nothing is loaded.
+		int acknowledge_interrupt();
+
+		struct InterruptDelegate {
+			/// Informs the delegate of a change in the interrupt line of the nominated MFP.
+			virtual void mfp68901_did_change_interrupt_status(MFP68901 *) = 0;
+		};
+		/// Sets a delegate that will be notified upon any change in the interrupt line.
+		void set_interrupt_delegate(InterruptDelegate *delegate);
+
+		// ClockingHint::Source.
+		ClockingHint::Preference preferred_clocking() final;
+
+	private:
+		// MARK: - Timers
+		enum class TimerMode {
+			Stopped, EventCount, Delay, PulseWidth
+		};
+		void set_timer_mode(int timer, TimerMode, int prescale, bool reset_timer);
+		void set_timer_data(int timer, uint8_t);
+		uint8_t get_timer_data(int timer);
+		void decrement_timer(int timer, int amount);
+
+		struct Timer {
+			TimerMode mode = TimerMode::Stopped;
+			uint8_t value = 0;
+			uint8_t reload_value = 0;
+			int prescale = 1;
+			int prescale_count = 1;
+			bool event_input = false;
+		} timers_[4];
+		uint8_t timer_ab_control_[2] = { 0, 0 };
+		uint8_t timer_cd_control_ = 0;
+
+		HalfCycles cycles_left_;
+
+		// MARK: - GPIP
+		uint8_t gpip_input_ = 0;
+		uint8_t gpip_output_ = 0;
+		uint8_t gpip_active_edge_ = 0;
+		uint8_t gpip_direction_ = 0;
+		uint8_t gpip_interrupt_state_ = 0;
+
+		void reevaluate_gpip_interrupts();
+
+		// MARK: - Interrupts
+
+		InterruptDelegate *interrupt_delegate_ = nullptr;
+
+		// Ad hoc documentation:
+		//
+		// An interrupt becomes pending if it is enabled at the time it occurs.
+		//
+		// If a pending interrupt is enabled in the interrupt mask, a processor
+		// interrupt is generated. Otherwise no processor interrupt is generated.
+		//
+		// (Disabling a bit in the enabled mask also instantaneously clears anything
+		// in the pending mask.)
+		//
+		// The user can write to the pending interrupt register; a write
+		// masks whatever is there — so you can disable bits but you cannot set them.
+		//
+		// If the vector register's 'S' bit is set then software end-of-interrupt mode applies:
+		// Acknowledgement of an interrupt clears that interrupt's pending bit, but also sets
+		// its in-service bit. That bit will remain set until the user writes a zero to its position.
+		// If any bits are set in the in-service register, then they will prevent lower-priority
+		// interrupts from being signalled to the CPU. Further interrupts of the same or a higher
+		// priority may occur.
+		//
+		// If the vector register's 'S' bit is clear then automatic end-of-interrupt mode applies:
+		// Acknowledgement of an interrupt will automatically clear the corresponding
+		// pending bit.
+		//
+		int interrupt_enable_ = 0;
+		int interrupt_pending_ = 0;
+		int interrupt_mask_ = 0;
+		int interrupt_in_service_ = 0;
+		bool interrupt_line_ = false;
+		uint8_t interrupt_vector_ = 0;
+
+		enum Interrupt {
+			GPIP0				= (1 << 0),
+			GPIP1				= (1 << 1),
+			GPIP2				= (1 << 2),
+			GPIP3				= (1 << 3),
+			TimerD				= (1 << 4),
+			TimerC				= (1 << 5),
+			GPIP4				= (1 << 6),
+			GPIP5				= (1 << 7),
+
+			TimerB				= (1 << 8),
+			TransmitError		= (1 << 9),
+			TransmitBufferEmpty	= (1 << 10),
+			ReceiveError		= (1 << 11),
+			ReceiveBufferFull	= (1 << 12),
+			TimerA				= (1 << 13),
+			GPIP6				= (1 << 14),
+			GPIP7				= (1 << 15),
+		};
+		void begin_interrupts(int interrupt);
+		void end_interrupts(int interrupt);
+		void update_interrupts();
+
+		/// @returns the most significant bit set in v, assuming it is one of the least significant 16.
+		inline static int msb16(int v) {
+			// Saturate all bits below the MSB.
+			v |= v >> 1;
+			v |= v >> 2;
+			v |= v >> 4;
+			v |= v >> 8;
+
+			// Throw away lesser bits.
+			return (v+1) >> 1;
+		}
+};
+
+}
+}
+
+#endif /* MFP68901_hpp */

Components/8255/i8255.hpp

@@ -27,7 +27,7 @@ template <class T> class i8255 {
 			Stores the value @c value to the register at @c address. If this causes a change in 8255 output
 			then the PortHandler will be informed.
 		*/
-		void set_register(int address, uint8_t value) {
+		void write(int address, uint8_t value) {
 			switch(address & 3) {
 				case 0:
 					if(!(control_ & 0x10)) {
@@ -60,7 +60,7 @@ template <class T> class i8255 {
 			Obtains the current value for the register at @c address. If this provides a reading
 			of input then the PortHandler will be queried.
 		*/
-		uint8_t get_register(int address) {
+		uint8_t read(int address) {
 			switch(address & 3) {
 				case 0:	return (control_ & 0x10) ? port_handler_.get_value(0) : outputs_[0];
 				case 1:	return (control_ & 0x02) ? port_handler_.get_value(1) : outputs_[1];

Components/8272/i8272.cpp

@@ -95,11 +95,11 @@ void i8272::run_for(Cycles cycles) {
 
 	// check for an expired timer
 	if(delay_time_ > 0) {
-		if(cycles.as_int() >= delay_time_) {
+		if(cycles.as_integral() >= delay_time_) {
 			delay_time_ = 0;
 			posit_event(static_cast<int>(Event8272::Timer));
 		} else {
-			delay_time_ -= cycles.as_int();
+			delay_time_ -= cycles.as_integral();
 		}
 	}
 
@@ -108,8 +108,8 @@ void i8272::run_for(Cycles cycles) {
 		int drives_left = drives_seeking_;
 		for(int c = 0; c < 4; c++) {
 			if(drives_[c].phase == Drive::Seeking) {
-				drives_[c].step_rate_counter += cycles.as_int();
-				int steps = drives_[c].step_rate_counter / (8000 * step_rate_time_);
+				drives_[c].step_rate_counter += cycles.as_integral();
+				auto steps = drives_[c].step_rate_counter / (8000 * step_rate_time_);
 				drives_[c].step_rate_counter %= (8000 * step_rate_time_);
 				while(steps--) {
 					// Perform a step.
@@ -141,12 +141,12 @@ void i8272::run_for(Cycles cycles) {
 			int head = c&1;
 
 			if(drives_[drive].head_unload_delay[head] > 0) {
-				if(cycles.as_int() >= drives_[drive].head_unload_delay[head]) {
+				if(cycles.as_integral() >= drives_[drive].head_unload_delay[head]) {
 					drives_[drive].head_unload_delay[head] = 0;
 					drives_[drive].head_is_loaded[head] = false;
 					head_timers_running_--;
 				} else {
-					drives_[drive].head_unload_delay[head] -= cycles.as_int();
+					drives_[drive].head_unload_delay[head] -= cycles.as_integral();
 				}
 				timers_left--;
 				if(!timers_left) break;
@@ -163,7 +163,7 @@ void i8272::run_for(Cycles cycles) {
 	if(is_sleeping_) update_clocking_observer();
 }
 
-void i8272::set_register(int address, uint8_t value) {
+void i8272::write(int address, uint8_t value) {
 	// don't consider attempted sets to the status register
 	if(!address) return;
 
@@ -181,7 +181,7 @@ void i8272::set_register(int address, uint8_t value) {
 	}
 }
 
-uint8_t i8272::get_register(int address) {
+uint8_t i8272::read(int address) {
 	if(address) {
 		if(result_stack_.empty()) return 0xff;
 		uint8_t result = result_stack_.back();
@@ -292,7 +292,7 @@ void i8272::posit_event(int event_type) {
 			WAIT_FOR_EVENT(Event8272::CommandByte)
 			SetBusy();
 
-			static const std::size_t required_lengths[32] = {
+			static constexpr std::size_t required_lengths[32] = {
 				0,	0,	9,	3,	2,	9,	9,	2,
 				1,	9,	2,	0,	9,	6,	0,	3,
 				0,	9,	0,	0,	0,	0,	0,	0,
@@ -865,7 +865,7 @@ void i8272::posit_event(int event_type) {
 			SetDataRequest();
 			SetDataDirectionToProcessor();
 
-			// The actual stuff of unwinding result_stack_ is handled by ::get_register; wait
+			// The actual stuff of unwinding result_stack_ is handled by ::read; wait
 			// until the processor has read all result bytes.
 			WAIT_FOR_EVENT(Event8272::ResultEmpty);
 

Components/8272/i8272.hpp

@@ -24,7 +24,7 @@ class BusHandler {
 		virtual void set_interrupt(bool irq) {}
 };
 
-class i8272: public Storage::Disk::MFMController {
+class i8272 : public Storage::Disk::MFMController {
 	public:
 		i8272(BusHandler &bus_handler, Cycles clock_rate);
 
@@ -33,13 +33,13 @@ class i8272: public Storage::Disk::MFMController {
 		void set_data_input(uint8_t value);
 		uint8_t get_data_output();
 
-		void set_register(int address, uint8_t value);
-		uint8_t get_register(int address);
+		void write(int address, uint8_t value);
+		uint8_t read(int address);
 
 		void set_dma_acknowledge(bool dack);
 		void set_terminal_count(bool tc);
 
-		ClockingHint::Preference preferred_clocking() override;
+		ClockingHint::Preference preferred_clocking() final;
 
 	protected:
 		virtual void select_drive(int number) = 0;
@@ -73,7 +73,7 @@ class i8272: public Storage::Disk::MFMController {
 		bool is_access_command_ = false;
 
 		// The counter used for ::Timer events.
-		int delay_time_ = 0;
+		Cycles::IntType delay_time_ = 0;
 
 		// The connected drives.
 		struct Drive {
@@ -89,12 +89,12 @@ class i8272: public Storage::Disk::MFMController {
 			bool seek_failed = false;
 
 			// Seeking: transient state.
-			int step_rate_counter = 0;
+			Cycles::IntType step_rate_counter = 0;
 			int steps_taken = 0;
 			int target_head_position = 0;	// either an actual number, or -1 to indicate to step until track zero
 
 			// Head state.
-			int head_unload_delay[2] = {0, 0};
+			Cycles::IntType head_unload_delay[2] = {0, 0};
 			bool head_is_loaded[2] = {false, false};
 
 		} drives_[4];

Components/8530/z8530.cpp

@@ -0,0 +1,268 @@
+//
+//  8530.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 07/06/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "z8530.hpp"
+
+#include "../../Outputs/Log.hpp"
+
+using namespace Zilog::SCC;
+
+void z8530::reset() {
+	// TODO.
+}
+
+bool z8530::get_interrupt_line() {
+	return
+		(master_interrupt_control_ & 0x8) &&
+		(
+			channels_[0].get_interrupt_line() ||
+			channels_[1].get_interrupt_line()
+		);
+}
+
+std::uint8_t z8530::read(int address) {
+	if(address & 2) {
+		// Read data register for channel
+		return 0x00;
+	} else {
+		// Read control register for channel.
+		uint8_t result = 0;
+
+		switch(pointer_) {
+			default:
+				result = channels_[address & 1].read(address & 2, pointer_);
+			break;
+
+			case 2:		// Handled non-symmetrically between channels.
+				if(address & 1) {
+					LOG("[SCC] Unimplemented: register 2 status bits");
+				} else {
+					result = interrupt_vector_;
+
+					// Modify the vector if permitted.
+//					if(master_interrupt_control_ & 1) {
+						for(int port = 0; port < 2; ++port) {
+							// TODO: the logic below assumes that DCD is the only implemented interrupt. Fix.
+							if(channels_[port].get_interrupt_line()) {
+								const uint8_t shift = 1 + 3*((master_interrupt_control_ & 0x10) >> 4);
+								const uint8_t mask = uint8_t(~(7 << shift));
+								result = uint8_t(
+									(result & mask) |
+									((1 | ((port == 1) ? 4 : 0)) << shift)
+								);
+								break;
+							}
+						}
+//					}
+				}
+			break;
+		}
+
+		pointer_ = 0;
+		update_delegate();
+		return result;
+	}
+
+	return 0x00;
+}
+
+void z8530::write(int address, std::uint8_t value) {
+	if(address & 2) {
+		// Write data register for channel.
+	} else {
+		// Write control register for channel.
+
+		// Most registers are per channel, but a couple are shared; sever
+		// them here.
+		switch(pointer_) {
+			default:
+				channels_[address & 1].write(address & 2, pointer_, value);
+			break;
+
+			case 2:	// Interrupt vector register; shared between both channels.
+				interrupt_vector_ = value;
+				LOG("[SCC] Interrupt vector set to " << PADHEX(2) << int(value));
+			break;
+
+			case 9:	// Master interrupt and reset register; also shared between both channels.
+				LOG("[SCC] Master interrupt and reset register: " << PADHEX(2) << int(value));
+				master_interrupt_control_ = value;
+			break;
+		}
+
+		// The pointer number resets to 0 after every access, but if it is zero
+		// then crib at least the next set of pointer bits (which, similarly, are shared
+		// between the two channels).
+		if(pointer_) {
+			pointer_ = 0;
+		} else {
+			// The lowest three bits are the lowest three bits of the pointer.
+			pointer_ = value & 7;
+
+			// If the command part of the byte is a 'point high', also set the
+			// top bit of the pointer.
+			if(((value >> 3)&7) == 1) {
+				pointer_ |= 8;
+			}
+		}
+	}
+	update_delegate();
+}
+
+void z8530::set_dcd(int port, bool level) {
+	channels_[port].set_dcd(level);
+	update_delegate();
+}
+
+// MARK: - Channel implementations
+
+uint8_t z8530::Channel::read(bool data, uint8_t pointer) {
+	// If this is a data read, just return it.
+	if(data) {
+		return data_;
+	} else {
+		// Otherwise, this is a control read...
+		switch(pointer) {
+			default:
+				LOG("[SCC] Unrecognised control read from register " << int(pointer));
+			return 0x00;
+
+			case 0:
+			return dcd_ ? 0x8 : 0x0;
+
+			case 0xf:
+			return external_interrupt_status_;
+		}
+	}
+
+	return 0x00;
+}
+
+void z8530::Channel::write(bool data, uint8_t pointer, uint8_t value) {
+	if(data) {
+		data_ = value;
+		return;
+	} else {
+		switch(pointer) {
+			default:
+				LOG("[SCC] Unrecognised control write: " << PADHEX(2) << int(value) << " to register " << int(pointer));
+			break;
+
+			case 0x0:	// Write register 0 — CRC reset and other functions.
+				// Decode CRC reset instructions.
+				switch(value >> 6) {
+					default:	/* Do nothing. */		break;
+					case 1:
+						LOG("[SCC] TODO: reset Rx CRC checker.");
+					break;
+					case 2:
+						LOG("[SCC] TODO: reset Tx CRC checker.");
+					break;
+					case 3:
+						LOG("[SCC] TODO: reset Tx underrun/EOM latch.");
+					break;
+				}
+
+				// Decode command code.
+				switch((value >> 3)&7) {
+					default:	/* Do nothing. */		break;
+					case 2:
+//						LOG("[SCC] reset ext/status interrupts.");
+						external_status_interrupt_ = false;
+						external_interrupt_status_ = 0;
+					break;
+					case 3:
+						LOG("[SCC] TODO: send abort (SDLC).");
+					break;
+					case 4:
+						LOG("[SCC] TODO: enable interrupt on next Rx character.");
+					break;
+					case 5:
+						LOG("[SCC] TODO: reset Tx interrupt pending.");
+					break;
+					case 6:
+						LOG("[SCC] TODO: reset error.");
+					break;
+					case 7:
+						LOG("[SCC] TODO: reset highest IUS.");
+					break;
+				}
+			break;
+
+			case 0x1:	// Write register 1 — Transmit/Receive Interrupt and Data Transfer Mode Definition.
+				interrupt_mask_ = value;
+			break;
+
+			case 0x4:	// Write register 4 — Transmit/Receive Miscellaneous Parameters and Modes.
+				// Bits 0 and 1 select parity mode.
+				if(!(value&1)) {
+					parity_ = Parity::Off;
+				} else {
+					parity_ = (value&2) ? Parity::Even : Parity::Odd;
+				}
+
+				// Bits 2 and 3 select stop bits.
+				switch((value >> 2)&3) {
+					default:	stop_bits_ = StopBits::Synchronous;			break;
+					case 1:		stop_bits_ = StopBits::OneBit;				break;
+					case 2:		stop_bits_ = StopBits::OneAndAHalfBits;		break;
+					case 3:		stop_bits_ = StopBits::TwoBits;				break;
+				}
+
+				// Bits 4 and 5 pick a sync mode.
+				switch((value >> 4)&3) {
+					default:	sync_mode_ = Sync::Monosync;	break;
+					case 1:		sync_mode_ = Sync::Bisync;		break;
+					case 2:		sync_mode_ = Sync::SDLC;		break;
+					case 3:		sync_mode_ = Sync::External;	break;
+				}
+
+				// Bits 6 and 7 select a clock rate multiplier, unless synchronous
+				// mode is enabled (and this is ignored if sync mode is external).
+				if(stop_bits_ == StopBits::Synchronous) {
+					clock_rate_multiplier_ = 1;
+				} else {
+					switch((value >> 6)&3) {
+						default:	clock_rate_multiplier_ = 1;		break;
+						case 1:		clock_rate_multiplier_ = 16;	break;
+						case 2:		clock_rate_multiplier_ = 32;	break;
+						case 3:		clock_rate_multiplier_ = 64;	break;
+					}
+				}
+			break;
+
+			case 0xf:	// Write register 15 — External/Status Interrupt Control.
+				external_interrupt_mask_ = value;
+			break;
+		}
+	}
+}
+
+void z8530::Channel::set_dcd(bool level) {
+	if(dcd_ == level) return;
+	dcd_ = level;
+
+	if(external_interrupt_mask_ & 0x8) {
+		external_status_interrupt_ = true;
+		external_interrupt_status_ |= 0x8;
+	}
+}
+
+bool z8530::Channel::get_interrupt_line() {
+	return
+		(interrupt_mask_ & 1) && external_status_interrupt_;
+	// TODO: other potential causes of an interrupt.
+}
+
+void z8530::update_delegate() {
+	const bool interrupt_line = get_interrupt_line();
+	if(interrupt_line != previous_interrupt_line_) {
+		previous_interrupt_line_ = interrupt_line;
+		if(delegate_) delegate_->did_change_interrupt_status(this, interrupt_line);
+	}
+}

Components/8530/z8530.hpp

@@ -0,0 +1,99 @@
+//
+//  z8530.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 07/06/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef z8530_hpp
+#define z8530_hpp
+
+#include <cstdint>
+
+namespace Zilog {
+namespace SCC {
+
+/*!
+	Models the Zilog 8530 SCC, a serial adaptor.
+*/
+class z8530 {
+	public:
+		/*
+			**Interface for emulated machine.**
+
+			Notes on addressing below:
+
+			There's no inherent ordering of the two 'address' lines,
+			A/B and C/D, but the methods below assume:
+
+				A/B = A0
+				C/D = A1
+		*/
+		std::uint8_t read(int address);
+		void write(int address, std::uint8_t value);
+		void reset();
+		bool get_interrupt_line();
+
+		struct Delegate {
+			virtual void did_change_interrupt_status(z8530 *, bool new_status) = 0;
+		};
+		void set_delegate(Delegate *delegate) {
+			delegate_ = delegate;
+		}
+
+		/*
+			**Interface for serial port input.**
+		*/
+		void set_dcd(int port, bool level);
+
+	private:
+		class Channel {
+			public:
+				uint8_t read(bool data, uint8_t pointer);
+				void write(bool data, uint8_t pointer, uint8_t value);
+				void set_dcd(bool level);
+				bool get_interrupt_line();
+
+			private:
+				uint8_t data_ = 0xff;
+
+				enum class Parity {
+					Even, Odd, Off
+				} parity_ = Parity::Off;
+
+				enum class StopBits {
+					Synchronous, OneBit, OneAndAHalfBits, TwoBits
+				} stop_bits_ = StopBits::Synchronous;
+
+				enum class Sync {
+					Monosync, Bisync, SDLC, External
+				} sync_mode_ = Sync::Monosync;
+
+				int clock_rate_multiplier_ = 1;
+
+				uint8_t interrupt_mask_ = 0;			// i.e. Write Register 0x1.
+
+				uint8_t external_interrupt_mask_ = 0;	// i.e. Write Register 0xf.
+				bool external_status_interrupt_ = false;
+				uint8_t external_interrupt_status_ = 0;
+
+				bool dcd_ = false;
+		} channels_[2];
+
+		uint8_t pointer_ = 0;
+
+		uint8_t interrupt_vector_ = 0;
+
+		uint8_t master_interrupt_control_ = 0;
+
+		bool previous_interrupt_line_ = false;
+		void update_delegate();
+		Delegate *delegate_ = nullptr;
+};
+
+}
+}
+
+
+#endif /* z8530_hpp */

Components/9918/9918.hpp

@@ -17,6 +17,7 @@
 #include <cstdint>
 
 namespace TI {
+namespace TMS {
 
 /*!
 	Provides emulation of the TMS9918a, TMS9928 and TMS9929. Likely in the future to be the
@@ -29,30 +30,22 @@ namespace TI {
 	These chips have only one non-on-demand interaction with the outside world: an interrupt line.
 	See get_time_until_interrupt and get_interrupt_line for asynchronous operation options.
 */
-class TMS9918: public TMS9918Base {
+class TMS9918: public Base {
 	public:
-		enum Personality {
-			TMS9918A,	// includes the 9928 and 9929; set TV standard and output device as desired.
-		};
-
 		/*!
 			Constructs an instance of the drive controller that behaves according to personality @c p.
 			@param p The type of controller to emulate.
 		*/
 		TMS9918(Personality p);
 
-		enum TVStandard {
-			/*! i.e. 50Hz output at around 312.5 lines/field */
-			PAL,
-			/*! i.e. 60Hz output at around 262.5 lines/field */
-			NTSC
-		};
-
 		/*! Sets the TV standard for this TMS, if that is hard-coded in hardware. */
 		void set_tv_standard(TVStandard standard);
 
-		/*! Provides the CRT this TMS is connected to. */
-		Outputs::CRT::CRT *get_crt();
+		/*! Sets the scan target this TMS will post content to. */
+		void set_scan_target(Outputs::Display::ScanTarget *);
+
+		/*! Sets the type of display the CRT will request. */
+		void set_display_type(Outputs::Display::DisplayType);
 
 		/*!
 			Runs the VCP for the number of cycles indicate; it is an implicit assumption of the code
@@ -61,26 +54,46 @@ class TMS9918: public TMS9918Base {
 		void run_for(const HalfCycles cycles);
 
 		/*! Sets a register value. */
-		void set_register(int address, uint8_t value);
+		void write(int address, uint8_t value);
 
 		/*! Gets a register value. */
-		uint8_t get_register(int address);
+		uint8_t read(int address);
+
+		/*! Gets the current scan line; provided by the Master System only. */
+		uint8_t get_current_line();
+
+		/*! Gets the current latched horizontal counter; provided by the Master System only. */
+		uint8_t get_latched_horizontal_counter();
+
+		/*! Latches the current horizontal counter. */
+		void latch_horizontal_counter();
 
 		/*!
-			Returns the amount of time until get_interrupt_line would next return true if
-			there are no interceding calls to set_register or get_register.
+			Returns the amount of time until @c get_interrupt_line would next return true if
+			there are no interceding calls to @c write or to @c read.
 
 			If get_interrupt_line is true now, returns zero. If get_interrupt_line would
 			never return true, returns -1.
 		*/
 		HalfCycles get_time_until_interrupt();
 
+		/*!
+			Returns the amount of time until the nominated line interrupt position is
+			reached on line @c line. If no line interrupt position is defined for
+			this VDP, returns the time until the 'beginning' of that line, whatever
+			that may mean.
+
+			@line is relative to the first pixel line of the display and may be negative.
+		*/
+		HalfCycles get_time_until_line(int line);
+
 		/*!
 			@returns @c true if the interrupt line is currently active; @c false otherwise.
 		*/
 		bool get_interrupt_line();
 };
 
-};
+}
+}
 
 #endif /* TMS9918_hpp */

Components/9918/Implementation/9918Base.hpp

@@ -12,90 +12,848 @@
 #include "../../../Outputs/CRT/CRT.hpp"
 #include "../../../ClockReceiver/ClockReceiver.hpp"
 
+#include <cassert>
 #include <cstdint>
 #include <memory>
+#include <vector>
 
 namespace TI {
+namespace TMS {
+
+enum Personality {
+	TMS9918A,	// includes the 9928 and 9929; set TV standard and output device as desired.
+	V9938,
+	V9958,
+	SMSVDP,
+	SMS2VDP,
+	GGVDP,
+};
+
+enum class TVStandard {
+	/*! i.e. 50Hz output at around 312.5 lines/field */
+	PAL,
+	/*! i.e. 60Hz output at around 262.5 lines/field */
+	NTSC
+};
+
+#define is_sega_vdp(x) ((x) >= SMSVDP)
+
+class Base {
+	public:
+		static const uint32_t palette_pack(uint8_t r, uint8_t g, uint8_t b) {
+			uint32_t result = 0;
+			uint8_t *const result_ptr = reinterpret_cast<uint8_t *>(&result);
+			result_ptr[0] = r;
+			result_ptr[1] = g;
+			result_ptr[2] = b;
+			result_ptr[3] = 0;
+			return result;
+		}
 
-class TMS9918Base {
 	protected:
-		TMS9918Base();
+		const static int output_lag = 11;	// i.e. pixel output will occur 11 cycles after corresponding data read.
 
-		std::unique_ptr<Outputs::CRT::CRT> crt_;
+		// The default TMS palette.
+		const uint32_t palette[16] = {
+			palette_pack(0, 0, 0),
+			palette_pack(0, 0, 0),
+			palette_pack(33, 200, 66),
+			palette_pack(94, 220, 120),
 
-		uint8_t ram_[16384];
+			palette_pack(84, 85, 237),
+			palette_pack(125, 118, 252),
+			palette_pack(212, 82, 77),
+			palette_pack(66, 235, 245),
 
+			palette_pack(252, 85, 84),
+			palette_pack(255, 121, 120),
+			palette_pack(212, 193, 84),
+			palette_pack(230, 206, 128),
+
+			palette_pack(33, 176, 59),
+			palette_pack(201, 91, 186),
+			palette_pack(204, 204, 204),
+			palette_pack(255, 255, 255)
+		};
+
+		Base(Personality p);
+
+		const Personality personality_;
+		Outputs::CRT::CRT crt_;
+		TVStandard tv_standard_ = TVStandard::NTSC;
+
+		// Holds the contents of this VDP's connected DRAM.
+		std::vector<uint8_t> ram_;
+
+		// Holds the state of the DRAM/CRAM-access mechanism.
 		uint16_t ram_pointer_ = 0;
 		uint8_t read_ahead_buffer_ = 0;
 		enum class MemoryAccess {
 			Read, Write, None
 		} queued_access_ = MemoryAccess::None;
+		int cycles_until_access_ = 0;
+		int minimum_access_column_ = 0;
+		int vram_access_delay() {
+			// This seems to be correct for all currently-modelled VDPs;
+			// it's the delay between an external device scheduling a
+			// read or write and the very first time that can occur
+			// (though, in practice, it won't happen until the next
+			// external slot after this number of cycles after the
+			// device has requested the read or write).
+			return 6;
+		}
 
+		// Holds the main status register.
 		uint8_t status_ = 0;
 
-		bool write_phase_ = false;
-		uint8_t low_write_ = 0;
+		// Current state of programmer input.
+		bool write_phase_ = false;	// Determines whether the VDP is expecting the low or high byte of a write.
+		uint8_t low_write_ = 0;		// Buffers the low byte of a write.
 
-		// The various register flags.
-		int next_screen_mode_ = 0, screen_mode_ = 0;
-		bool next_blank_screen_ = true, blank_screen_ = true;
+		// Various programmable flags.
+		bool mode1_enable_ = false;
+		bool mode2_enable_ = false;
+		bool mode3_enable_ = false;
+		bool blank_display_ = false;
 		bool sprites_16x16_ = false;
 		bool sprites_magnified_ = false;
 		bool generate_interrupts_ = false;
 		int sprite_height_ = 8;
-		uint16_t pattern_name_address_ = 0;
-		uint16_t colour_table_address_ = 0;
-		uint16_t pattern_generator_table_address_ = 0;
-		uint16_t sprite_attribute_table_address_ = 0;
-		uint16_t sprite_generator_table_address_ = 0;
+
+		size_t pattern_name_address_ = 0;				// i.e. address of the tile map.
+		size_t colour_table_address_ = 0;				// address of the colour map (if applicable).
+		size_t pattern_generator_table_address_ = 0;	// address of the tile contents.
+		size_t sprite_attribute_table_address_ = 0;		// address of the sprite list.
+		size_t sprite_generator_table_address_ = 0;		// address of the sprite contents.
 
 		uint8_t text_colour_ = 0;
 		uint8_t background_colour_ = 0;
 
-		HalfCycles half_cycles_into_frame_;
-		int column_ = 0, row_ = 0, output_column_ = 0;
+		// This implementation of this chip officially accepts a 3.58Mhz clock, but runs
+		// internally at 5.37Mhz. The following two help to maintain a lossless conversion
+		// from the one to the other.
 		int cycles_error_ = 0;
-		uint32_t *pixel_target_ = nullptr, *pixel_base_ = nullptr;
+		HalfCycles half_cycles_before_internal_cycles(int internal_cycles);
 
-		void output_border(int cycles);
+		// Internal mechanisms for position tracking.
+		int latched_column_ = 0;
 
-		// Vertical timing details.
-		int frame_lines_ = 262;
-		int first_vsync_line_ = 227;
+		// A helper function to output the current border colour for
+		// the number of cycles supplied.
+		void output_border(int cycles, uint32_t cram_dot);
+
+		// A struct to contain timing information for the current mode.
+		struct {
+			/*
+				Vertical layout:
+
+				Lines 0 to [pixel_lines]: standard data fetch and drawing will occur.
+				... to [first_vsync_line]: refresh fetches will occur and border will be output.
+				.. to [2.5 or 3 lines later]: vertical sync is output.
+				... to [total lines - 1]: refresh fetches will occur and border will be output.
+				... for one line: standard data fetch will occur, without drawing.
+			*/
+			int total_lines = 262;
+			int pixel_lines = 192;
+			int first_vsync_line = 227;
+
+			// Maximum number of sprite slots to populate;
+			// if sprites beyond this number should be visible
+			// then the appropriate status information will be set.
+			int maximum_visible_sprites = 4;
+
+			// Set the position, in cycles, of the two interrupts,
+			// within a line.
+			struct {
+				int column = 4;
+				int row = 193;
+			} end_of_frame_interrupt_position;
+			int line_interrupt_position = -1;
+
+			// Enables or disabled the recognition of the sprite
+			// list terminator, and sets the terminator value.
+			bool allow_sprite_terminator = true;
+			uint8_t sprite_terminator = 0xd0;
+		} mode_timing_;
+
+		uint8_t line_interrupt_target = 0xff;
+		uint8_t line_interrupt_counter = 0;
+		bool enable_line_interrupts_ = false;
+		bool line_interrupt_pending_ = false;
+
+		// The screen mode is a necessary predecessor to picking the line mode,
+		// which is the thing latched per line.
+		enum class ScreenMode {
+			Blank,
+			Text,
+			MultiColour,
+			ColouredText,
+			Graphics,
+			SMSMode4
+		} screen_mode_;
 
-		// Horizontal selections.
 		enum class LineMode {
-			Text = 0,
-			Character = 1,
-			Refresh = 2
-		} line_mode_ = LineMode::Text;
-		int first_pixel_column_, first_right_border_column_;
+			Text,
+			Character,
+			Refresh,
+			SMS
+		};
 
-		uint8_t pattern_names_[40];
-		uint8_t pattern_buffer_[40];
-		uint8_t colour_buffer_[40];
+		// Temporary buffers collect a representation of this line prior to pixel serialisation.
+		struct LineBuffer {
+			// The line mode describes the proper timing diagram for this line.
+			LineMode line_mode = LineMode::Text;
 
-		struct SpriteSet {
+			// Holds the horizontal scroll position to apply to this line;
+			// of those VDPs currently implemented, affects the Master System only.
+			uint8_t latched_horizontal_scroll = 0;
+
+			// The names array holds pattern names, as an offset into memory, and
+			// potentially flags also.
+			struct {
+				size_t offset = 0;
+				uint8_t flags = 0;
+			} names[40];
+
+			// The patterns array holds tile patterns, corresponding 1:1 with names.
+			// Four bytes per pattern is the maximum required by any
+			// currently-implemented VDP.
+			uint8_t patterns[40][4];
+
+			/*
+				Horizontal layout (on a 342-cycle clock):
+
+					15 cycles right border
+					58 cycles blanking & sync
+					13 cycles left border
+
+					... i.e. to cycle 86, then:
+
+					border up to first_pixel_output_column;
+					pixels up to next_border_column;
+					border up to the end.
+
+				e.g. standard 256-pixel modes will want to set
+				first_pixel_output_column = 86, next_border_column = 342.
+			*/
+			int first_pixel_output_column = 94;
+			int next_border_column = 334;
+
+			// An active sprite is one that has been selected for composition onto
+			// this line.
 			struct ActiveSprite {
-				int index = 0;
-				int row = 0;
+				int index = 0;		// The original in-table index of this sprite.
+				int row = 0;		// The row of the sprite that should be drawn.
+				int x = 0;			// The sprite's x position on screen.
 
-				uint8_t info[4];
-				uint8_t image[2];
+				uint8_t image[4];		// Up to four bytes of image information.
+				int shift_position = 0;	// An offset representing how much of the image information has already been drawn.
+			} active_sprites[8];
 
-				int shift_position = 0;
-			} active_sprites[4];
-			int active_sprite_slot = 0;
-		} sprite_sets_[2];
-		int active_sprite_set_ = 0;
-		bool sprites_stopped_ = false;
+			int active_sprite_slot = 0;		// A pointer to the slot into which a new active sprite will be deposited, if required.
+			bool sprites_stopped = false;	// A special TMS feature is that a sentinel value can be used to prevent any further sprites
+											// being evaluated for display. This flag determines whether the sentinel has yet been reached.
 
-		int access_pointer_ = 0;
+			void reset_sprite_collection();
+		} line_buffers_[313];
+		void posit_sprite(LineBuffer &buffer, int sprite_number, int sprite_y, int screen_row);
 
-		inline void test_sprite(int sprite_number, int screen_row);
-		inline void get_sprite_contents(int start, int cycles, int screen_row);
+		// There is a delay between reading into the line buffer and outputting from there to the screen. That delay
+		// is observeable because reading time affects availability of memory accesses and therefore time in which
+		// to update sprites and tiles, but writing time affects when the palette is used and when the collision flag
+		// may end up being set. So the two processes are slightly decoupled. The end of reading one line may overlap
+		// with the beginning of writing the next, hence the two separate line buffers.
+		struct LineBufferPointer {
+			int row, column;
+		} read_pointer_, write_pointer_;
+
+		// The SMS VDP has a programmer-set colour palette, with a dedicated patch of RAM. But the RAM is only exactly
+		// fast enough for the pixel clock. So when the programmer writes to it, that causes a one-pixel glitch; there
+		// isn't the bandwidth for the read both write to occur simultaneously. The following buffer therefore keeps
+		// track of pending collisions, for visual reproduction.
+		struct CRAMDot {
+			LineBufferPointer location;
+			uint32_t value;
+		};
+		std::vector<CRAMDot> upcoming_cram_dots_;
+
+		// Extra information that affects the Master System output mode.
+		struct {
+			// Programmer-set flags.
+			bool vertical_scroll_lock = false;
+			bool horizontal_scroll_lock = false;
+			bool hide_left_column = false;
+			bool shift_sprites_8px_left = false;
+			bool mode4_enable = false;
+			uint8_t horizontal_scroll = 0;
+			uint8_t vertical_scroll = 0;
+
+			// The Master System's additional colour RAM.
+			uint32_t colour_ram[32];
+			bool cram_is_selected = false;
+
+			// Holds the vertical scroll position for this frame; this is latched
+			// once and cannot dynamically be changed until the next frame.
+			uint8_t latched_vertical_scroll = 0;
+
+			size_t pattern_name_address;
+			size_t sprite_attribute_table_address;
+			size_t sprite_generator_table_address;
+		} master_system_;
+
+		void set_current_screen_mode() {
+			if(blank_display_) {
+				screen_mode_ = ScreenMode::Blank;
+				return;
+			}
+
+			if(is_sega_vdp(personality_) && master_system_.mode4_enable) {
+				screen_mode_ = ScreenMode::SMSMode4;
+				mode_timing_.maximum_visible_sprites = 8;
+				return;
+			}
+
+			mode_timing_.maximum_visible_sprites = 4;
+			if(!mode1_enable_ && !mode2_enable_ && !mode3_enable_) {
+				screen_mode_ = ScreenMode::ColouredText;
+				return;
+			}
+
+			if(mode1_enable_ && !mode2_enable_ && !mode3_enable_) {
+				screen_mode_ = ScreenMode::Text;
+				return;
+			}
+
+			if(!mode1_enable_ && mode2_enable_ && !mode3_enable_) {
+				screen_mode_ = ScreenMode::Graphics;
+				return;
+			}
+
+			if(!mode1_enable_ && !mode2_enable_ && mode3_enable_) {
+				screen_mode_ = ScreenMode::MultiColour;
+				return;
+			}
+
+			// TODO: undocumented TMS modes.
+			screen_mode_ = ScreenMode::Blank;
+		}
+
+		void do_external_slot(int access_column) {
+			// Don't do anything if the required time for the access to become executable
+			// has yet to pass.
+			if(access_column < minimum_access_column_) {
+				return;
+			}
+
+			switch(queued_access_) {
+				default: return;
+
+				case MemoryAccess::Write:
+					if(master_system_.cram_is_selected) {
+						// Adjust the palette.
+						master_system_.colour_ram[ram_pointer_ & 0x1f] = palette_pack(
+							static_cast<uint8_t>(((read_ahead_buffer_ >> 0) & 3) * 255 / 3),
+							static_cast<uint8_t>(((read_ahead_buffer_ >> 2) & 3) * 255 / 3),
+							static_cast<uint8_t>(((read_ahead_buffer_ >> 4) & 3) * 255 / 3)
+						);
+
+						// Schedule a CRAM dot; this is scheduled for wherever it should appear
+						// on screen. So it's wherever the output stream would be now. Which
+						// is output_lag cycles ago from the point of view of the input stream.
+						upcoming_cram_dots_.emplace_back();
+						CRAMDot &dot = upcoming_cram_dots_.back();
+
+						dot.location.column = write_pointer_.column - output_lag;
+						dot.location.row = write_pointer_.row;
+
+						// Handle before this row conditionally; then handle after (or, more realistically,
+						// exactly at the end of) naturally.
+						if(dot.location.column < 0) {
+							--dot.location.row;
+							dot.location.column += 342;
+						}
+						dot.location.row += dot.location.column / 342;
+						dot.location.column %= 342;
+
+						dot.value = master_system_.colour_ram[ram_pointer_ & 0x1f];
+					} else {
+						ram_[ram_pointer_ & 16383] = read_ahead_buffer_;
+					}
+				break;
+				case MemoryAccess::Read:
+					read_ahead_buffer_ = ram_[ram_pointer_ & 16383];
+				break;
+			}
+			++ram_pointer_;
+			queued_access_ = MemoryAccess::None;
+		}
+
+/*
+	Fetching routines follow below; they obey the following rules:
+
+		1)	input is a start position and an end position; they should perform the proper
+			operations for the period: start <= time < end.
+		2)	times are measured relative to a 172-cycles-per-line clock (so: they directly
+			count access windows on the TMS and Master System).
+		3)	time 0 is the beginning of the access window immediately after the last pattern/data
+			block fetch that would contribute to this line, in a normal 32-column mode. So:
+
+				* it's cycle 309 on Mattias' TMS diagram;
+				* it's cycle 1238 on his V9938 diagram;
+				* it's after the last background render block in Mask of Destiny's Master System timing diagram.
+
+			That division point was selected, albeit arbitrarily, because it puts all the tile
+			fetches for a single line into the same [0, 171] period.
+
+		4)	all of these functions are templated with a `use_end` parameter. That will be true if
+			end is < 172, false otherwise. So functions can use it to eliminate should-exit-not checks,
+			for the more usual path of execution.
+
+	Provided for the benefit of the methods below:
+
+		*	the function external_slot(), which will perform any pending VRAM read/write.
+		*	the macros slot(n) and external_slot(n) which can be used to schedule those things inside a
+			switch(start)-based implementation.
+
+	All functions should just spool data to intermediary storage. This is because for most VDPs there is
+	a decoupling between fetch pattern and output pattern, and it's neater to keep the same division
+	for the exceptions.
+*/
+
+#define slot(n)	\
+		if(use_end && end == n) return;\
+		case n
+
+#define external_slot(n)	\
+	slot(n): do_external_slot((n)*2);
+
+#define external_slots_2(n)	\
+	external_slot(n);		\
+	external_slot(n+1);
+
+#define external_slots_4(n)	\
+	external_slots_2(n);	\
+	external_slots_2(n+2);
+
+#define external_slots_8(n)	\
+	external_slots_4(n);	\
+	external_slots_4(n+4);
+
+#define external_slots_16(n)	\
+	external_slots_8(n);		\
+	external_slots_8(n+8);
+
+#define external_slots_32(n)	\
+	external_slots_16(n);		\
+	external_slots_16(n+16);
+
+
+/***********************************************
+             TMS9918 Fetching Code
+************************************************/
+
+		template<bool use_end> void fetch_tms_refresh(int start, int end) {
+#define refresh(location)		\
+	slot(location):				\
+	external_slot(location+1);
+
+#define refreshes_2(location)	\
+	refresh(location);			\
+	refresh(location+2);
+
+#define refreshes_4(location)	\
+	refreshes_2(location);		\
+	refreshes_2(location+4);
+
+#define refreshes_8(location)	\
+	refreshes_4(location);		\
+	refreshes_4(location+8);
+
+			switch(start) {
+				default: assert(false);
+
+				/* 44 external slots */
+				external_slots_32(0)
+				external_slots_8(32)
+				external_slots_4(40)
+
+				/* 64 refresh/external slot pairs (= 128 windows) */
+				refreshes_8(44);
+				refreshes_8(60);
+				refreshes_8(76);
+				refreshes_8(92);
+				refreshes_8(108);
+				refreshes_8(124);
+				refreshes_8(140);
+				refreshes_8(156);
+
+				return;
+			}
+
+#undef refreshes_8
+#undef refreshes_4
+#undef refreshes_2
+#undef refresh
+		}
+
+		template<bool use_end> void fetch_tms_text(int start, int end) {
+#define fetch_tile_name(location, column)		slot(location): line_buffer.names[column].offset = ram_[row_base + column];
+#define fetch_tile_pattern(location, column)	slot(location): line_buffer.patterns[column][0] = ram_[row_offset + size_t(line_buffer.names[column].offset << 3)];
+
+#define fetch_column(location, column)	\
+	fetch_tile_name(location, column);	\
+	external_slot(location+1);	\
+	fetch_tile_pattern(location+2, column);
+
+#define fetch_columns_2(location, column)	\
+	fetch_column(location, column);	\
+	fetch_column(location+3, column+1);
+
+#define fetch_columns_4(location, column)	\
+	fetch_columns_2(location, column);	\
+	fetch_columns_2(location+6, column+2);
+
+#define fetch_columns_8(location, column)	\
+	fetch_columns_4(location, column);	\
+	fetch_columns_4(location+12, column+4);
+
+			LineBuffer &line_buffer = line_buffers_[write_pointer_.row];
+			const size_t row_base = pattern_name_address_ & (0x3c00 | static_cast<size_t>(write_pointer_.row >> 3) * 40);
+			const size_t row_offset = pattern_generator_table_address_ & (0x3800 | (write_pointer_.row & 7));
+
+			switch(start) {
+				default: assert(false);
+
+					/* 47 external slots (= 47 windows) */
+					external_slots_32(0)
+					external_slots_8(32)
+					external_slots_4(40)
+					external_slots_2(44)
+					external_slot(46)
+
+					/* 40 column fetches (= 120 windows) */
+					fetch_columns_8(47, 0);
+					fetch_columns_8(71, 8);
+					fetch_columns_8(95, 16);
+					fetch_columns_8(119, 24);
+					fetch_columns_8(143, 32);
+
+					/* 5 more external slots */
+					external_slots_4(167);
+					external_slot(171);
+
+				return;
+			}
+
+#undef fetch_columns_8
+#undef fetch_columns_4
+#undef fetch_columns_2
+#undef fetch_column
+#undef fetch_tile_pattern
+#undef fetch_tile_name
+		}
+
+		template<bool use_end> void fetch_tms_character(int start, int end) {
+#define sprite_fetch_coordinates(location, sprite)	\
+	slot(location):		\
+	slot(location+1):	\
+		line_buffer.active_sprites[sprite].x = \
+			ram_[\
+				sprite_attribute_table_address_ & size_t(0x3f81 | (line_buffer.active_sprites[sprite].index << 2))\
+			];
+
+		// This implementation doesn't refetch Y; it's unclear to me
+		// whether it's refetched.
+
+#define sprite_fetch_graphics(location, sprite)	\
+	slot(location):		\
+	slot(location+1):	\
+	slot(location+2):	\
+	slot(location+3):	{\
+		const uint8_t name = ram_[\
+				sprite_attribute_table_address_ & size_t(0x3f82 | (line_buffer.active_sprites[sprite].index << 2))\
+			] & (sprites_16x16_ ? ~3 : ~0);\
+		line_buffer.active_sprites[sprite].image[2] = ram_[\
+				sprite_attribute_table_address_ & size_t(0x3f83 | (line_buffer.active_sprites[sprite].index << 2))\
+			];\
+		line_buffer.active_sprites[sprite].x -= (line_buffer.active_sprites[sprite].image[2] & 0x80) >> 2;\
+		const size_t graphic_location = sprite_generator_table_address_ & size_t(0x3800 | (name << 3) | line_buffer.active_sprites[sprite].row);	\
+		line_buffer.active_sprites[sprite].image[0] = ram_[graphic_location];\
+		line_buffer.active_sprites[sprite].image[1] = ram_[graphic_location+16];\
+	}
+
+#define sprite_fetch_block(location, sprite)	\
+	sprite_fetch_coordinates(location, sprite)	\
+	sprite_fetch_graphics(location+2, sprite)
+
+#define sprite_y_read(location, sprite)	\
+	slot(location): posit_sprite(sprite_selection_buffer, sprite, ram_[sprite_attribute_table_address_ & (((sprite) << 2) | 0x3f80)], write_pointer_.row);
+
+#define fetch_tile_name(column) line_buffer.names[column].offset = ram_[(row_base + column) & 0x3fff];
+
+#define fetch_tile(column)	{\
+		line_buffer.patterns[column][1] = ram_[(colour_base + size_t((line_buffer.names[column].offset << 3) >> colour_name_shift)) & 0x3fff];		\
+		line_buffer.patterns[column][0] = ram_[(pattern_base + size_t(line_buffer.names[column].offset << 3)) & 0x3fff];	\
+	}
+
+#define background_fetch_block(location, column, sprite)	\
+	slot(location):	fetch_tile_name(column)		\
+	external_slot(location+1);	\
+	slot(location+2):	\
+	slot(location+3): fetch_tile(column)	\
+	slot(location+4): fetch_tile_name(column+1)	\
+	sprite_y_read(location+5, sprite);	\
+	slot(location+6):	\
+	slot(location+7): fetch_tile(column+1)	\
+	slot(location+8): fetch_tile_name(column+2)	\
+	sprite_y_read(location+9, sprite+1);	\
+	slot(location+10):	\
+	slot(location+11): fetch_tile(column+2)	\
+	slot(location+12): fetch_tile_name(column+3)	\
+	sprite_y_read(location+13, sprite+2);	\
+	slot(location+14):	\
+	slot(location+15): fetch_tile(column+3)
+
+			LineBuffer &line_buffer = line_buffers_[write_pointer_.row];
+			LineBuffer &sprite_selection_buffer = line_buffers_[(write_pointer_.row + 1) % mode_timing_.total_lines];
+			const size_t row_base = pattern_name_address_ & (size_t((write_pointer_.row << 2)&~31) | 0x3c00);
+
+			size_t pattern_base = pattern_generator_table_address_;
+			size_t colour_base = colour_table_address_;
+			int colour_name_shift = 6;
+
+			if(screen_mode_ == ScreenMode::Graphics) {
+				// If this is high resolution mode, allow the row number to affect the pattern and colour addresses.
+				pattern_base &= size_t(0x2000 | ((write_pointer_.row & 0xc0) << 5));
+				colour_base &= size_t(0x2000 | ((write_pointer_.row & 0xc0) << 5));
+
+				colour_base += size_t(write_pointer_.row & 7);
+				colour_name_shift = 0;
+			} else {
+				colour_base &= size_t(0xffc0);
+				pattern_base &= size_t(0x3800);
+			}
+
+			if(screen_mode_ == ScreenMode::MultiColour) {
+				pattern_base += size_t((write_pointer_.row >> 2) & 7);
+			} else {
+				pattern_base += size_t(write_pointer_.row & 7);
+			}
+
+			switch(start) {
+				default: assert(false);
+
+				external_slots_2(0);
+
+				sprite_fetch_block(2, 0);
+				sprite_fetch_block(8, 1);
+				sprite_fetch_coordinates(14, 2);
+
+				external_slots_4(16);
+				external_slot(20);
+
+				sprite_fetch_graphics(21, 2);
+				sprite_fetch_block(25, 3);
+
+				slot(31):
+					sprite_selection_buffer.reset_sprite_collection();
+					do_external_slot(31*2);
+				external_slots_2(32);
+				external_slot(34);
+
+				sprite_y_read(35, 0);
+				sprite_y_read(36, 1);
+				sprite_y_read(37, 2);
+				sprite_y_read(38, 3);
+				sprite_y_read(39, 4);
+				sprite_y_read(40, 5);
+				sprite_y_read(41, 6);
+				sprite_y_read(42, 7);
+
+				background_fetch_block(43, 0, 8);
+				background_fetch_block(59, 4, 11);
+				background_fetch_block(75, 8, 14);
+				background_fetch_block(91, 12, 17);
+				background_fetch_block(107, 16, 20);
+				background_fetch_block(123, 20, 23);
+				background_fetch_block(139, 24, 26);
+				background_fetch_block(155, 28, 29);
+
+				return;
+			}
+
+#undef background_fetch_block
+#undef fetch_tile
+#undef fetch_tile_name
+#undef sprite_y_read
+#undef sprite_fetch_block
+#undef sprite_fetch_graphics
+#undef sprite_fetch_coordinates
+		}
+
+
+/***********************************************
+          Master System Fetching Code
+************************************************/
+
+		template<bool use_end> void fetch_sms(int start, int end) {
+#define sprite_fetch(sprite)	{\
+		line_buffer.active_sprites[sprite].x = \
+			ram_[\
+				master_system_.sprite_attribute_table_address & size_t(0x3f80 | (line_buffer.active_sprites[sprite].index << 1))\
+			] - (master_system_.shift_sprites_8px_left ? 8 : 0);	\
+		const uint8_t name = ram_[\
+				master_system_.sprite_attribute_table_address & size_t(0x3f81 | (line_buffer.active_sprites[sprite].index << 1))\
+			] & (sprites_16x16_ ? ~1 : ~0);\
+		const size_t graphic_location = master_system_.sprite_generator_table_address & size_t(0x2000 | (name << 5) | (line_buffer.active_sprites[sprite].row << 2));	\
+		line_buffer.active_sprites[sprite].image[0] = ram_[graphic_location];	\
+		line_buffer.active_sprites[sprite].image[1] = ram_[graphic_location+1];	\
+		line_buffer.active_sprites[sprite].image[2] = ram_[graphic_location+2];	\
+		line_buffer.active_sprites[sprite].image[3] = ram_[graphic_location+3];	\
+	}
+
+#define sprite_fetch_block(location, sprite)	\
+	slot(location):		\
+	slot(location+1):	\
+	slot(location+2):	\
+	slot(location+3):	\
+	slot(location+4):	\
+	slot(location+5):	\
+		sprite_fetch(sprite);\
+		sprite_fetch(sprite+1);
+
+#define sprite_y_read(location, sprite)	\
+	slot(location):	\
+		posit_sprite(sprite_selection_buffer, sprite, ram_[master_system_.sprite_attribute_table_address & ((sprite) | 0x3f00)], write_pointer_.row);	\
+		posit_sprite(sprite_selection_buffer, sprite+1, ram_[master_system_.sprite_attribute_table_address & ((sprite + 1) | 0x3f00)], write_pointer_.row);	\
+
+#define fetch_tile_name(column, row_info)	{\
+		const size_t scrolled_column = (column - horizontal_offset) & 0x1f;\
+		const size_t address = row_info.pattern_address_base + (scrolled_column << 1);	\
+		line_buffer.names[column].flags = ram_[address+1];	\
+		line_buffer.names[column].offset = static_cast<size_t>(	\
+			(((line_buffer.names[column].flags&1) << 8) | ram_[address]) << 5	\
+		) + row_info.sub_row[(line_buffer.names[column].flags&4) >> 2];	\
+	}
+
+#define fetch_tile(column)	\
+	line_buffer.patterns[column][0] = ram_[line_buffer.names[column].offset];	\
+	line_buffer.patterns[column][1] = ram_[line_buffer.names[column].offset+1];	\
+	line_buffer.patterns[column][2] = ram_[line_buffer.names[column].offset+2];	\
+	line_buffer.patterns[column][3] = ram_[line_buffer.names[column].offset+3];
+
+#define background_fetch_block(location, column, sprite, row_info)	\
+	slot(location):	fetch_tile_name(column, row_info)		\
+	external_slot(location+1);					\
+	slot(location+2):	\
+	slot(location+3):	\
+	slot(location+4):	\
+		fetch_tile(column)					\
+		fetch_tile_name(column+1, row_info)			\
+		sprite_y_read(location+5, sprite);	\
+	slot(location+6):	\
+	slot(location+7):	\
+	slot(location+8):	\
+		fetch_tile(column+1)					\
+		fetch_tile_name(column+2, row_info)				\
+		sprite_y_read(location+9, sprite+2);	\
+	slot(location+10):	\
+	slot(location+11):	\
+	slot(location+12):	\
+		fetch_tile(column+2)					\
+		fetch_tile_name(column+3, row_info)				\
+		sprite_y_read(location+13, sprite+4);	\
+	slot(location+14):	\
+	slot(location+15): fetch_tile(column+3)
+
+			// Determine the coarse horizontal scrolling offset; this isn't applied on the first two lines if the programmer has requested it.
+			LineBuffer &line_buffer = line_buffers_[write_pointer_.row];
+			LineBuffer &sprite_selection_buffer = line_buffers_[(write_pointer_.row + 1) % mode_timing_.total_lines];
+			const int horizontal_offset = (write_pointer_.row >= 16 || !master_system_.horizontal_scroll_lock) ? (line_buffer.latched_horizontal_scroll >> 3) : 0;
+
+			// Limit address bits in use if this is a SMS2 mode.
+			const bool is_tall_mode = mode_timing_.pixel_lines != 192;
+			const size_t pattern_name_address = master_system_.pattern_name_address | (is_tall_mode ? 0x800 : 0);
+			const size_t pattern_name_offset = is_tall_mode ? 0x100 : 0;
+
+			// Determine row info for the screen both (i) if vertical scrolling is applied; and (ii) if it isn't.
+			// The programmer can opt out of applying vertical scrolling to the right-hand portion of the display.
+			const int scrolled_row = (write_pointer_.row + master_system_.latched_vertical_scroll) % (is_tall_mode ? 256 : 224);
+			struct RowInfo {
+				size_t pattern_address_base;
+				size_t sub_row[2];
+			};
+			const RowInfo scrolled_row_info = {
+				(pattern_name_address & size_t(((scrolled_row & ~7) << 3) | 0x3800)) - pattern_name_offset,
+				{static_cast<size_t>((scrolled_row & 7) << 2), 28 ^ static_cast<size_t>((scrolled_row & 7) << 2)}
+			};
+			RowInfo row_info;
+			if(master_system_.vertical_scroll_lock) {
+				row_info.pattern_address_base = (pattern_name_address & size_t(((write_pointer_.row & ~7) << 3) | 0x3800)) - pattern_name_offset;
+				row_info.sub_row[0] = size_t((write_pointer_.row & 7) << 2);
+				row_info.sub_row[1] = 28 ^ size_t((write_pointer_.row & 7) << 2);
+			} else row_info = scrolled_row_info;
+
+			// ... and do the actual fetching, which follows this routine:
+			switch(start) {
+				default: assert(false);
+
+				sprite_fetch_block(0, 0);
+				sprite_fetch_block(6, 2);
+
+				external_slots_4(12);
+				external_slot(16);
+
+				sprite_fetch_block(17, 4);
+				sprite_fetch_block(23, 6);
+
+				slot(29):
+					sprite_selection_buffer.reset_sprite_collection();
+					do_external_slot(29*2);
+				external_slot(30);
+
+				sprite_y_read(31, 0);
+				sprite_y_read(32, 2);
+				sprite_y_read(33, 4);
+				sprite_y_read(34, 6);
+				sprite_y_read(35, 8);
+				sprite_y_read(36, 10);
+				sprite_y_read(37, 12);
+				sprite_y_read(38, 14);
+
+				background_fetch_block(39, 0, 16, scrolled_row_info);
+				background_fetch_block(55, 4, 22, scrolled_row_info);
+				background_fetch_block(71, 8, 28, scrolled_row_info);
+				background_fetch_block(87, 12, 34, scrolled_row_info);
+				background_fetch_block(103, 16, 40, scrolled_row_info);
+				background_fetch_block(119, 20, 46, scrolled_row_info);
+				background_fetch_block(135, 24, 52, row_info);
+				background_fetch_block(151, 28, 58, row_info);
+
+				external_slots_4(167);
+
+				return;
+			}
+
+#undef background_fetch_block
+#undef fetch_tile
+#undef fetch_tile_name
+#undef sprite_y_read
+#undef sprite_fetch_block
+#undef sprite_fetch
+		}
+
+#undef external_slot
+#undef slot
+
+		uint32_t *pixel_target_ = nullptr, *pixel_origin_ = nullptr;
+		bool asked_for_write_area_ = false;
+		void draw_tms_character(int start, int end);
+		void draw_tms_text(int start, int end);
+		void draw_sms(int start, int end, uint32_t cram_dot);
 };
 
+}
 }
 
 #endif /* TMS9918Base_hpp */

Components/AY38910/AY38910.cpp

@@ -12,45 +12,56 @@
 
 using namespace GI::AY38910;
 
-AY38910::AY38910(Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_(task_queue) {
-	// set up envelope lookup tables
+AY38910::AY38910(Personality personality, Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_(task_queue) {
+	// Don't use the low bit of the envelope position if this is an AY.
+	envelope_position_mask_ |= personality == Personality::AY38910;
+
+	// Set up envelope lookup tables.
 	for(int c = 0; c < 16; c++) {
-		for(int p = 0; p < 32; p++) {
+		for(int p = 0; p < 64; p++) {
 			switch(c) {
 				case 0: case 1: case 2: case 3: case 9:
-					envelope_shapes_[c][p] = (p < 16) ? (p^0xf) : 0;
-					envelope_overflow_masks_[c] = 0x1f;
+					/* Envelope: \____ */
+					envelope_shapes_[c][p] = (p < 32) ? (p^0x1f) : 0;
+					envelope_overflow_masks_[c] = 0x3f;
 				break;
 				case 4: case 5: case 6: case 7: case 15:
-					envelope_shapes_[c][p] = (p < 16) ? p : 0;
-					envelope_overflow_masks_[c] = 0x1f;
+					/* Envelope: /____ */
+					envelope_shapes_[c][p] = (p < 32) ? p : 0;
+					envelope_overflow_masks_[c] = 0x3f;
 				break;
 
 				case 8:
-					envelope_shapes_[c][p] = (p & 0xf) ^ 0xf;
+					/* Envelope: \\\\\\\\ */
+					envelope_shapes_[c][p] = (p & 0x1f) ^ 0x1f;
 					envelope_overflow_masks_[c] = 0x00;
 				break;
 				case 12:
-					envelope_shapes_[c][p] = (p & 0xf);
+					/* Envelope: //////// */
+					envelope_shapes_[c][p] = (p & 0x1f);
 					envelope_overflow_masks_[c] = 0x00;
 				break;
 
 				case 10:
-					envelope_shapes_[c][p] = (p & 0xf) ^ ((p < 16) ? 0xf : 0x0);
+					/* Envelope: \/\/\/\/ */
+					envelope_shapes_[c][p] = (p & 0x1f) ^ ((p < 32) ? 0x1f : 0x0);
 					envelope_overflow_masks_[c] = 0x00;
 				break;
 				case 14:
-					envelope_shapes_[c][p] = (p & 0xf) ^ ((p < 16) ? 0x0 : 0xf);
+					/* Envelope: /\/\/\/\ */
+					envelope_shapes_[c][p] = (p & 0x1f) ^ ((p < 32) ? 0x0 : 0x1f);
 					envelope_overflow_masks_[c] = 0x00;
 				break;
 
 				case 11:
-					envelope_shapes_[c][p] = (p < 16) ? (p^0xf) : 0xf;
-					envelope_overflow_masks_[c] = 0x1f;
+					/* Envelope: \------	(if - is high) */
+					envelope_shapes_[c][p] = (p < 32) ? (p^0x1f) : 0x1f;
+					envelope_overflow_masks_[c] = 0x3f;
 				break;
 				case 13:
-					envelope_shapes_[c][p] = (p < 16) ? p : 0xf;
-					envelope_overflow_masks_[c] = 0x1f;
+					/* Envelope: /------- */
+					envelope_shapes_[c][p] = (p < 32) ? p : 0x1f;
+					envelope_overflow_masks_[c] = 0x3f;
 				break;
 			}
 		}
@@ -61,18 +72,27 @@ AY38910::AY38910(Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_
 
 void AY38910::set_sample_volume_range(std::int16_t range) {
 	// set up volume lookup table
-	const float max_volume = static_cast<float>(range) / 3.0f;	// As there are three channels.
-	const float root_two = sqrtf(2.0f);
-	for(int v = 0; v < 16; v++) {
-		volumes_[v] = static_cast<int>(max_volume / powf(root_two, static_cast<float>(v ^ 0xf)));
+	const float max_volume = float(range) / 3.0f;	// As there are three channels.
+	constexpr float root_two = 1.414213562373095f;
+	for(int v = 0; v < 32; v++) {
+		volumes_[v] = int(max_volume / powf(root_two, float(v ^ 0x1f) / 2.0f));
 	}
-	volumes_[0] = 0;
+	volumes_[0] = 0;	// Tie level 0 to silence.
 	evaluate_output_volume();
 }
 
 void AY38910::get_samples(std::size_t number_of_samples, int16_t *target) {
+	// Note on structure below: the real AY has a built-in divider of 8
+	// prior to applying its tone and noise dividers. But the YM fills the
+	// same total periods for noise and tone with double-precision envelopes.
+	// Therefore this class implements a divider of 4 and doubles the tone
+	// and noise periods. The envelope ticks along at the divide-by-four rate,
+	// but if this is an AY rather than a YM then its lowest bit is forced to 1,
+	// matching the YM datasheet's depiction of envelope level 31 as equal to
+	// programmatic volume 15, envelope level 29 as equal to programmatic 14, etc.
+
 	std::size_t c = 0;
-	while((master_divider_&7) && c < number_of_samples) {
+	while((master_divider_&3) && c < number_of_samples) {
 		target[c] = output_volume_;
 		master_divider_++;
 		c++;
@@ -83,49 +103,49 @@ void AY38910::get_samples(std::size_t number_of_samples, int16_t *target) {
 	if(tone_counters_[c]) tone_counters_[c]--;\
 	else {\
 		tone_outputs_[c] ^= 1;\
-		tone_counters_[c] = tone_periods_[c];\
+		tone_counters_[c] = tone_periods_[c] << 1;\
 	}
 
-		// update the tone channels
+		// Update the tone channels.
 		step_channel(0);
 		step_channel(1);
 		step_channel(2);
 
 #undef step_channel
 
-		// ... the noise generator. This recomputes the new bit repeatedly but harmlessly, only shifting
+		// Update the noise generator. This recomputes the new bit repeatedly but harmlessly, only shifting
 		// it into the official 17 upon divider underflow.
 		if(noise_counter_) noise_counter_--;
 		else {
-			noise_counter_ = noise_period_;
+			noise_counter_ = noise_period_ << 1;	// To cover the double resolution of envelopes.
 			noise_output_ ^= noise_shift_register_&1;
 			noise_shift_register_ |= ((noise_shift_register_ ^ (noise_shift_register_ >> 3))&1) << 17;
 			noise_shift_register_ >>= 1;
 		}
 
-		// ... and the envelope generator. Table based for pattern lookup, with a 'refill' step: a way of
-		// implementing non-repeating patterns by locking them to table position 0x1f.
+		// Update the envelope generator. Table based for pattern lookup, with a 'refill' step: a way of
+		// implementing non-repeating patterns by locking them to the final table position.
 		if(envelope_divider_) envelope_divider_--;
 		else {
 			envelope_divider_ = envelope_period_;
 			envelope_position_ ++;
-			if(envelope_position_ == 32) envelope_position_ = envelope_overflow_masks_[output_registers_[13]];
+			if(envelope_position_ == 64) envelope_position_ = envelope_overflow_masks_[output_registers_[13]];
 		}
 
 		evaluate_output_volume();
 
-		for(int ic = 0; ic < 8 && c < number_of_samples; ic++) {
+		for(int ic = 0; ic < 4 && c < number_of_samples; ic++) {
 			target[c] = output_volume_;
 			c++;
 			master_divider_++;
 		}
 	}
 
-	master_divider_ &= 7;
+	master_divider_ &= 3;
 }
 
 void AY38910::evaluate_output_volume() {
-	int envelope_volume = envelope_shapes_[output_registers_[13]][envelope_position_];
+	int envelope_volume = envelope_shapes_[output_registers_[13]][envelope_position_ | envelope_position_mask_];
 
 	// The output level for a channel is:
 	//	1 if neither tone nor noise is enabled;
@@ -142,9 +162,20 @@ void AY38910::evaluate_output_volume() {
 	};
 #undef level
 
-		// Channel volume is a simple selection: if the bit at 0x10 is set, use the envelope volume; otherwise use the lower four bits
+	// This remapping table seeks to map 'channel volumes', i.e. the levels produced from the
+	// 16-step progammatic volumes set per channel to 'envelope volumes', i.e. the 32-step
+	// volumes that are produced by the envelope generators (on a YM at least). My reading of
+	// the data sheet is that '0' is still off, but 15 should be as loud as peak envelope. So
+	// I've thrown in the discontinuity at the low end, where it'll be very quiet.
+	const int channel_volumes[] = {
+		0, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31
+	};
+	static_assert(sizeof(channel_volumes) == 16*sizeof(int));
+
+		// Channel volume is a simple selection: if the bit at 0x10 is set, use the envelope volume; otherwise use the lower four bits,
+		// mapped to the range 1–31 in case this is a YM.
 #define channel_volume(c)	\
-	((output_registers_[c] >> 4)&1) * envelope_volume + (((output_registers_[c] >> 4)&1)^1) * (output_registers_[c]&0xf)
+	((output_registers_[c] >> 4)&1) * envelope_volume + (((output_registers_[c] >> 4)&1)^1) * channel_volumes[output_registers_[c]&0xf]
 
 	const int volumes[3] = {
 		channel_volume(8),
@@ -173,11 +204,15 @@ void AY38910::select_register(uint8_t r) {
 }
 
 void AY38910::set_register_value(uint8_t value) {
+	// There are only 16 registers.
 	if(selected_register_ > 15) return;
-	registers_[selected_register_] = value;
+
+	// If this is a register that affects audio output, enqueue a mutation onto the
+	// audio generation thread.
 	if(selected_register_ < 14) {
-		int selected_register = selected_register_;
+		const int selected_register = selected_register_;
 		task_queue_.defer([=] () {
+			// Perform any register-specific mutation to output generation.
 			uint8_t masked_value = value;
 			switch(selected_register) {
 				case 0: case 2: case 4:
@@ -208,12 +243,34 @@ void AY38910::set_register_value(uint8_t value) {
 					envelope_position_ = 0;
 				break;
 			}
+
+			// Store a copy of the current register within the storage used by the audio generation
+			// thread, and apply any changes to output volume.
 			output_registers_[selected_register] = masked_value;
 			evaluate_output_volume();
 		});
-	} else {
-		if(port_handler_) port_handler_->set_port_output(selected_register_ == 15, value);
 	}
+
+	// Decide which outputs are going to need updating (if any).
+	bool update_port_a = false;
+	bool update_port_b = true;
+	if(port_handler_) {
+		if(selected_register_ == 7) {
+			const uint8_t io_change = registers_[7] ^ value;
+			update_port_b = !!(io_change&0x80);
+			update_port_a = !!(io_change&0x40);
+		} else {
+			update_port_b = selected_register_ == 15;
+			update_port_a = selected_register_ != 15;
+		}
+	}
+
+	// Keep a copy of the new value that is usable from the emulation thread.
+	registers_[selected_register_] = value;
+
+	// Update ports as required.
+	if(update_port_b) set_port_output(true);
+	if(update_port_a) set_port_output(false);
 }
 
 uint8_t AY38910::get_register_value() {
@@ -238,6 +295,8 @@ uint8_t AY38910::get_port_output(bool port_b) {
 
 void AY38910::set_port_handler(PortHandler *handler) {
 	port_handler_ = handler;
+	set_port_output(true);
+	set_port_output(false);
 }
 
 void AY38910::set_data_input(uint8_t r) {
@@ -245,6 +304,16 @@ void AY38910::set_data_input(uint8_t r) {
 	update_bus();
 }
 
+void AY38910::set_port_output(bool port_b) {
+	// Per the data sheet: "each [IO] pin is provided with an on-chip pull-up resistor,
+	// so that when in the "input" mode, all pins will read normally high". Therefore,
+	// report programmer selection of input mode as creating an output of 0xff.
+	if(port_handler_) {
+		const bool is_output = !!(registers_[7] & (port_b ? 0x80 : 0x40));
+		port_handler_->set_port_output(port_b, is_output ? registers_[port_b ? 15 : 14] : 0xff);
+	}
+}
+
 uint8_t AY38910::get_data_output() {
 	if(control_state_ == Read && selected_register_ >= 14 && selected_register_ < 16) {
 		// Per http://cpctech.cpc-live.com/docs/psgnotes.htm if a port is defined as output then the
@@ -253,7 +322,7 @@ uint8_t AY38910::get_data_output() {
 		const uint8_t mask = port_handler_ ? port_handler_->get_port_input(selected_register_ == 15) : 0xff;
 
 		switch(selected_register_) {
-			default: 	break;
+			default:	break;
 			case 14:	return mask & ((registers_[0x7] & 0x40) ? registers_[14] : 0xff);
 			case 15:	return mask & ((registers_[0x7] & 0x80) ? registers_[15] : 0xff);
 		}
@@ -280,7 +349,7 @@ void AY38910::update_bus() {
 	// Assume no output, unless this turns out to be a read.
 	data_output_ = 0xff;
 	switch(control_state_) {
-		default: 			break;
+		default:			break;
 		case LatchAddress:	select_register(data_input_);			break;
 		case Write:			set_register_value(data_input_);		break;
 		case Read:			data_output_ = get_register_value();	break;

Components/AY38910/AY38910.hpp

@@ -35,9 +35,10 @@ class PortHandler {
 		}
 
 		/*!
-			Requests the current input on an AY port.
+			Sets the current output on an AY port.
 
-			@param port_b @c true if the input being queried is Port B. @c false if it is Port A.
+			@param port_b @c true if the output being posted is Port B. @c false if it is Port A.
+			@param value the value now being output.
 		*/
 		virtual void set_port_output(bool port_b, uint8_t value) {}
 };
@@ -51,6 +52,13 @@ enum ControlLines {
 	BDIR	= (1 << 2)
 };
 
+enum class Personality {
+	/// Provides 16 volume levels to envelopes.
+	AY38910,
+	/// Provides 32 volume levels to envelopes.
+	YM2149F
+};
+
 /*!
 	Provides emulation of an AY-3-8910 / YM2149, which is a three-channel sound chip with a
 	noise generator and a volume envelope generator, which also provides two bidirectional
@@ -59,7 +67,7 @@ enum ControlLines {
 class AY38910: public ::Outputs::Speaker::SampleSource {
 	public:
 		/// Creates a new AY38910.
-		AY38910(Concurrency::DeferringAsyncTaskQueue &task_queue);
+		AY38910(Personality, Concurrency::DeferringAsyncTaskQueue &);
 
 		/// Sets the value the AY would read from its data lines if it were not outputting.
 		void set_data_input(uint8_t r);
@@ -83,7 +91,7 @@ class AY38910: public ::Outputs::Speaker::SampleSource {
 		*/
 		void set_port_handler(PortHandler *);
 
-		// to satisfy ::Outputs::Speaker (included via ::Outputs::Filter; not for public consumption
+		// to satisfy ::Outputs::Speaker (included via ::Outputs::Filter.
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		bool is_zero_level();
 		void set_sample_volume_range(std::int16_t range);
@@ -108,11 +116,11 @@ class AY38910: public ::Outputs::Speaker::SampleSource {
 
 		int envelope_period_ = 0;
 		int envelope_divider_ = 0;
-		int envelope_position_ = 0;
-		int envelope_shapes_[16][32];
+		int envelope_position_ = 0, envelope_position_mask_ = 0;
+		int envelope_shapes_[16][64];
 		int envelope_overflow_masks_[16];
 
-		int volumes_[16];
+		int volumes_[32];
 
 		enum ControlState {
 			Inactive,
@@ -128,10 +136,11 @@ class AY38910: public ::Outputs::Speaker::SampleSource {
 		uint8_t data_input_, data_output_;
 
 		int16_t output_volume_;
-		inline void evaluate_output_volume();
+		void evaluate_output_volume();
 
-		inline void update_bus();
+		void update_bus();
 		PortHandler *port_handler_ = nullptr;
+		void set_port_output(bool port_b);
 };
 
 }

Components/DiskII/DiskII.cpp

@@ -22,7 +22,7 @@ namespace  {
 DiskII::DiskII(int clock_rate) :
 	clock_rate_(clock_rate),
 	inputs_(input_command),
-	drives_{{static_cast<unsigned int>(clock_rate), 300, 1}, {static_cast<unsigned int>(clock_rate), 300, 1}}
+	drives_{{clock_rate, 300, 1}, {clock_rate, 300, 1}}
 {
 	drives_[0].set_clocking_hint_observer(this);
 	drives_[1].set_clocking_hint_observer(this);
@@ -78,7 +78,7 @@ void DiskII::select_drive(int drive) {
 void DiskII::run_for(const Cycles cycles) {
 	if(preferred_clocking() == ClockingHint::Preference::None) return;
 
-	int integer_cycles = cycles.as_int();
+	auto integer_cycles = cycles.as_integral();
 	while(integer_cycles--) {
 		const int address = (state_ & 0xf0) | inputs_ | ((shift_register_&0x80) >> 6);
 		if(flux_duration_) {
@@ -124,7 +124,7 @@ void DiskII::run_for(const Cycles cycles) {
 	// motor switch being flipped and the drive motor actually switching off.
 	// This models that, accepting overrun as a risk.
 	if(motor_off_time_ >= 0) {
-		motor_off_time_ -= cycles.as_int();
+		motor_off_time_ -= cycles.as_integral();
 		if(motor_off_time_ < 0) {
 			set_control(Control::Motor, false);
 		}
@@ -211,7 +211,7 @@ void DiskII::set_disk(const std::shared_ptr<Storage::Disk::Disk> &disk, int driv
 	drives_[drive].set_disk(disk);
 }
 
-void DiskII::process_event(const Storage::Disk::Track::Event &event) {
+void DiskII::process_event(const Storage::Disk::Drive::Event &event) {
 	if(event.type == Storage::Disk::Track::Event::FluxTransition) {
 		inputs_ &= ~input_flux;
 		flux_duration_ = 2;	// Upon detection of a flux transition, the flux flag should stay set for 1us. Emulate that as two cycles.
@@ -266,7 +266,7 @@ int DiskII::read_address(int address) {
 		break;
 		case 0xf:
 			if(!(inputs_ & input_mode))
-				drives_[active_drive_].begin_writing(Storage::Time(1, clock_rate_), false);
+				drives_[active_drive_].begin_writing(Storage::Time(1, int(clock_rate_)), false);
 			inputs_ |= input_mode;
 		break;
 	}

Components/DiskII/DiskII.hpp

@@ -26,7 +26,7 @@ namespace Apple {
 /*!
 	Provides an emulation of the Apple Disk II.
 */
-class DiskII:
+class DiskII final:
 	public Storage::Disk::Drive::EventDelegate,
 	public ClockingHint::Source,
 	public ClockingHint::Observer {
@@ -48,13 +48,13 @@ class DiskII:
 			The value returned by @c read_address if accessing that address
 			didn't cause the disk II to place anything onto the bus.
 		*/
-		const int DidNotLoad = -1;
+		static constexpr int DidNotLoad = -1;
 
 		/// Advances the controller by @c cycles.
 		void run_for(const Cycles cycles);
 
 		/*!
-		 	Supplies the image of the state machine (i.e. P6) ROM,
+			Supplies the image of the state machine (i.e. P6) ROM,
 			which dictates how the Disk II will respond to input.
 
 			To reduce processing costs, some assumptions are made by
@@ -76,7 +76,7 @@ class DiskII:
 		void set_disk(const std::shared_ptr<Storage::Disk::Disk> &disk, int drive);
 
 		// As per Sleeper.
-		ClockingHint::Preference preferred_clocking() override;
+		ClockingHint::Preference preferred_clocking() final;
 
 		// The Disk II functions as a potential target for @c Activity::Sources.
 		void set_activity_observer(Activity::Observer *observer);
@@ -98,10 +98,10 @@ class DiskII:
 		void select_drive(int drive);
 
 		uint8_t trigger_address(int address, uint8_t value);
-		void process_event(const Storage::Disk::Track::Event &event) override;
+		void process_event(const Storage::Disk::Drive::Event &event) override;
 		void set_component_prefers_clocking(ClockingHint::Source *component, ClockingHint::Preference preference) override;
 
-		const int clock_rate_ = 0;
+		const Cycles::IntType clock_rate_ = 0;
 
 		uint8_t state_ = 0;
 		uint8_t inputs_ = 0;
@@ -109,7 +109,7 @@ class DiskII:
 
 		int stepper_mask_ = 0;
 		int stepper_position_ = 0;
-		int motor_off_time_ = -1;
+		Cycles::IntType motor_off_time_ = -1;
 
 		bool is_write_protected();
 		std::array<uint8_t, 256> state_machine_;

Components/DiskII/IWM.cpp

@@ -0,0 +1,406 @@
+//
+//  IWM.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 05/05/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "IWM.hpp"
+
+#include "../../Outputs/Log.hpp"
+
+using namespace Apple;
+
+namespace  {
+	constexpr int CA0		= 1 << 0;
+	constexpr int CA1		= 1 << 1;
+	constexpr int CA2		= 1 << 2;
+	constexpr int LSTRB		= 1 << 3;
+	constexpr int ENABLE	= 1 << 4;
+	constexpr int DRIVESEL	= 1 << 5;	/* This means drive select, like on the original Disk II. */
+	constexpr int Q6		= 1 << 6;
+	constexpr int Q7		= 1 << 7;
+	constexpr int SEL		= 1 << 8;	/* This is an additional input, not available on a Disk II, with a confusingly-similar name to SELECT but a distinct purpose. */
+}
+
+IWM::IWM(int clock_rate) :
+	clock_rate_(clock_rate) {}
+
+// MARK: - Bus accessors
+
+uint8_t IWM::read(int address) {
+	access(address);
+
+	// Per Inside Macintosh:
+	//
+	// "Before you can read from any of the disk registers you must set up the state of the IWM so that it
+	// can pass the data through to the MC68000's address space where you'll be able to read it. To do that,
+	// you must first turn off Q7 by reading or writing dBase+q7L. Then turn on Q6 by accessing dBase+q6H.
+	// After that, the IWM will be able to pass data from the disk's RD/SENSE line through to you."
+	//
+	// My understanding:
+	//
+	//	Q6 = 1, Q7 = 0 reads the status register. The meaning of the top 'SENSE' bit is then determined by
+	//	the CA0,1,2 and SEL switches as described in Inside Macintosh, summarised above as RD/SENSE.
+
+	if(address&1) {
+		return 0xff;
+	}
+
+	switch(state_ & (Q6 | Q7 | ENABLE)) {
+		default:
+			LOG("[IWM] Invalid read\n");
+		return 0xff;
+
+		// "Read all 1s".
+//			printf("Reading all 1s\n");
+//		return 0xff;
+
+		case 0:
+		case ENABLE: {				/* Read data register. Zeroing afterwards is a guess. */
+			const auto result = data_register_;
+
+			if(data_register_ & 0x80) {
+//				printf("\n\nIWM:%02x\n\n", data_register_);
+//				printf(".");
+				data_register_ = 0;
+			}
+//			LOG("Reading data register: " << PADHEX(2) << int(result));
+
+			return result;
+		}
+
+		case Q6: case Q6|ENABLE: {
+			/*
+				[If A = 0], Read status register:
+
+				bits 0-4: same as mode register.
+				bit 5: 1 = either /ENBL1 or /ENBL2 is currently low.
+				bit 6: 1 = MZ (reserved for future compatibility; should always be read as 0).
+				bit 7: 1 = SENSE input high; 0 = SENSE input low.
+
+				(/ENBL1 is low when the first drive's motor is on; /ENBL2 is low when the second drive's motor is on.
+				If the 1-second timer is enabled, motors remain on for one second after being programmatically disabled.)
+			*/
+
+			return uint8_t(
+				(mode_&0x1f) |
+				((state_ & ENABLE) ? 0x20 : 0x00) |
+				(sense() & 0x80)
+			);
+		} break;
+
+		case Q7: case Q7|ENABLE:
+			/*
+				Read write-handshake register:
+
+				bits 0-5: reserved for future use (currently read as 1).
+				bit 6: 1 = write state (0 = underrun has occurred; 1 = no underrun so far).
+				bit 7: 1 = write data buffer ready for data (1 = ready; 0 = busy).
+			*/
+//			LOG("Reading write handshake: " << PADHEX(2) << (0x3f | write_handshake_));
+		return 0x3f | write_handshake_;
+	}
+
+	return 0xff;
+}
+
+void IWM::write(int address, uint8_t input) {
+	access(address);
+
+	switch(state_ & (Q6 | Q7 | ENABLE)) {
+		default: break;
+
+		case Q7|Q6:
+			/*
+				Write mode register:
+
+				bit 0: 1 = latch mode (should be set in asynchronous mode).
+				bit 1: 0 = synchronous handshake protocol; 1 = asynchronous.
+				bit 2: 0 = 1-second on-board timer enable; 1 = timer disable.
+				bit 3: 0 = slow mode; 1 = fast mode.
+				bit 4: 0 = 7Mhz; 1 = 8Mhz (7 or 8 mHz clock descriptor).
+				bit 5: 1 = test mode; 0 = normal operation.
+				bit 6: 1 = MZ-reset.
+				bit 7: reserved for future expansion.
+			*/
+
+			mode_ = input;
+
+			switch(mode_ & 0x18) {
+				case 0x00:		bit_length_ = Cycles(24);		break;	// slow mode, 7Mhz
+				case 0x08:		bit_length_ = Cycles(12);		break;	// fast mode, 7Mhz
+				case 0x10:		bit_length_ = Cycles(32);		break;	// slow mode, 8Mhz
+				case 0x18:		bit_length_ = Cycles(16);		break;	// fast mode, 8Mhz
+			}
+			LOG("IWM mode is now " << PADHEX(2) << int(mode_));
+		break;
+
+		case Q7|Q6|ENABLE:	// Write data register.
+			next_output_ = input;
+			write_handshake_ &= ~0x80;
+		break;
+	}
+}
+
+// MARK: - Switch access
+
+void IWM::access(int address) {
+	// Keep a record of switch state; bits in state_
+	// should correlate with the anonymous namespace constants
+	// defined at the top of this file — CA0, CA1, etc.
+	address &= 0xf;
+	const auto mask = 1 << (address >> 1);
+	const auto old_state = state_;
+
+	if(address & 1) {
+		state_ |= mask;
+	} else {
+		state_ &= ~mask;
+	}
+
+	// React appropriately to ENABLE and DRIVESEL changes, and changes into/out of write mode.
+	if(old_state != state_) {
+		push_drive_state();
+
+		switch(mask) {
+			default: break;
+
+			case ENABLE:
+				if(address & 1) {
+					if(drives_[active_drive_]) drives_[active_drive_]->set_enabled(true);
+				} else {
+					// If the 1-second delay is enabled, set up a timer for that.
+					if(!(mode_ & 4)) {
+						cycles_until_disable_ = Cycles(clock_rate_);
+					} else {
+						if(drives_[active_drive_]) drives_[active_drive_]->set_enabled(false);
+					}
+				}
+			break;
+
+			case DRIVESEL: {
+				const int new_drive = address & 1;
+				if(new_drive != active_drive_) {
+					if(drives_[active_drive_]) drives_[active_drive_]->set_enabled(false);
+					active_drive_ = new_drive;
+					if(drives_[active_drive_]) {
+						drives_[active_drive_]->set_enabled(state_ & ENABLE || (cycles_until_disable_ > Cycles(0)));
+						push_drive_state();
+					}
+				}
+			} break;
+
+			case Q6:
+			case Q7:
+				select_shift_mode();
+			break;
+		}
+	}
+}
+
+void IWM::set_select(bool enabled) {
+	// Store SEL as an extra state bit.
+	if(enabled) state_ |= SEL;
+	else state_ &= ~SEL;
+	push_drive_state();
+}
+
+void IWM::push_drive_state() {
+	if(drives_[active_drive_])  {
+		const uint8_t drive_control_lines =
+			((state_ & CA0) ? IWMDrive::CA0 : 0) |
+			((state_ & CA1) ? IWMDrive::CA1 : 0) |
+			((state_ & CA2) ? IWMDrive::CA2 : 0) |
+			((state_ & SEL) ? IWMDrive::SEL : 0) |
+			((state_ & LSTRB) ? IWMDrive::LSTRB : 0);
+		drives_[active_drive_]->set_control_lines(drive_control_lines);
+	}
+}
+
+// MARK: - Active logic
+
+void IWM::run_for(const Cycles cycles) {
+	// Check for a timeout of the motor-off timer.
+	if(cycles_until_disable_ > Cycles(0)) {
+		cycles_until_disable_ -= cycles;
+		if(cycles_until_disable_ <= Cycles(0)) {
+			cycles_until_disable_ = Cycles(0);
+			if(drives_[active_drive_])
+				drives_[active_drive_]->set_enabled(false);
+		}
+	}
+
+	// Activity otherwise depends on mode and motor state.
+	auto integer_cycles = cycles.as_integral();
+	switch(shift_mode_) {
+		case ShiftMode::Reading: {
+			// Per the IWM patent, column 7, around line 35 onwards: "The expected time
+			// is widened by approximately one-half an interval before and after the
+			// expected time since the data is not precisely spaced when read due to
+			// variations in drive speed and other external factors". The error_margin
+			// here implements the 'after' part of that contract.
+			const auto error_margin = Cycles(bit_length_.as_integral() >> 1);
+
+			if(drive_is_rotating_[active_drive_]) {
+				while(integer_cycles--) {
+					drives_[active_drive_]->run_for(Cycles(1));
+					++cycles_since_shift_;
+					if(cycles_since_shift_ == bit_length_ + error_margin) {
+						propose_shift(0);
+					}
+				}
+			} else {
+				while(cycles_since_shift_ + integer_cycles >= bit_length_ + error_margin) {
+					const auto run_length = bit_length_ + error_margin - cycles_since_shift_;
+					integer_cycles -= run_length.as_integral();
+					cycles_since_shift_ += run_length;
+					propose_shift(0);
+				}
+				cycles_since_shift_ += Cycles(integer_cycles);
+			}
+		} break;
+
+		case ShiftMode::Writing:
+			if(drives_[active_drive_]->is_writing()) {
+				while(cycles_since_shift_ + integer_cycles >= bit_length_) {
+					const auto cycles_until_write = bit_length_ - cycles_since_shift_;
+					drives_[active_drive_]->run_for(cycles_until_write);
+
+					// Output a flux transition if the top bit is set.
+					drives_[active_drive_]->write_bit(shift_register_ & 0x80);
+					shift_register_ <<= 1;
+
+					integer_cycles -= cycles_until_write.as_integral();
+					cycles_since_shift_ = Cycles(0);
+
+					--output_bits_remaining_;
+					if(!output_bits_remaining_) {
+						if(!(write_handshake_ & 0x80)) {
+							write_handshake_ |= 0x80;
+							shift_register_ = next_output_;
+							output_bits_remaining_ = 8;
+//							LOG("Next byte: " << PADHEX(2) << int(shift_register_));
+						} else {
+							write_handshake_ &= ~0x40;
+							drives_[active_drive_]->end_writing();
+//							printf("\n");
+							LOG("Overrun; done.");
+							select_shift_mode();
+						}
+					}
+				}
+
+				cycles_since_shift_ = integer_cycles;
+				if(integer_cycles) {
+					drives_[active_drive_]->run_for(cycles_since_shift_);
+				}
+			} else {
+				drives_[active_drive_]->run_for(cycles);
+			}
+		break;
+
+		case ShiftMode::CheckingWriteProtect:
+			if(integer_cycles < 8) {
+				shift_register_ = (shift_register_ >> integer_cycles) | (sense() & (0xff << (8 - integer_cycles)));
+			} else {
+				shift_register_ = sense();
+			}
+
+		/* Deliberate fallthrough. */
+		default:
+			if(drive_is_rotating_[active_drive_]) drives_[active_drive_]->run_for(cycles);
+		break;
+	}
+}
+
+void IWM::select_shift_mode() {
+	// Don't allow an ongoing write to be interrupted.
+	if(shift_mode_ == ShiftMode::Writing && drives_[active_drive_] && drives_[active_drive_]->is_writing()) return;
+
+	const auto old_shift_mode = shift_mode_;
+
+	switch(state_ & (Q6|Q7)) {
+		default:	shift_mode_ = ShiftMode::CheckingWriteProtect;		break;
+		case 0:		shift_mode_ = ShiftMode::Reading;					break;
+		case Q7:
+			// "The IWM is put into the write state by a transition from the write protect sense state to the
+			// write load state".
+			if(shift_mode_ == ShiftMode::CheckingWriteProtect) shift_mode_ = ShiftMode::Writing;
+		break;
+	}
+
+	// If writing mode just began, set the drive into write mode and cue up the first output byte.
+	if(drives_[active_drive_] && old_shift_mode != ShiftMode::Writing && shift_mode_ == ShiftMode::Writing) {
+		drives_[active_drive_]->begin_writing(Storage::Time(1, clock_rate_ / bit_length_.as_integral()), false);
+		shift_register_ = next_output_;
+		write_handshake_ |= 0x80 | 0x40;
+		output_bits_remaining_ = 8;
+		LOG("Seeding output with " << PADHEX(2) << shift_register_);
+	}
+}
+
+uint8_t IWM::sense() {
+	return drives_[active_drive_] ? (drives_[active_drive_]->read() ? 0xff : 0x00) : 0xff;
+}
+
+void IWM::process_event(const Storage::Disk::Drive::Event &event) {
+	if(shift_mode_ != ShiftMode::Reading) return;
+
+	switch(event.type) {
+		case Storage::Disk::Track::Event::IndexHole: return;
+		case Storage::Disk::Track::Event::FluxTransition:
+			propose_shift(1);
+		break;
+	}
+}
+
+void IWM::propose_shift(uint8_t bit) {
+	// TODO: synchronous mode.
+
+//	LOG("Shifting input");
+
+	// See above for text from the IWM patent, column 7, around line 35 onwards.
+	// The error_margin here implements the 'before' part of that contract.
+	//
+	// Basic effective logic: if at least 1 is fozund in the bit_length_ cycles centred
+	// on the current expected bit delivery time as implied by cycles_since_shift_,
+	// shift in a 1 and start a new window wherever the first found 1 was.
+	//
+	// If no 1s are found, shift in a 0 and don't alter expectations as to window placement.
+	const auto error_margin = Cycles(bit_length_.as_integral() >> 1);
+	if(bit && cycles_since_shift_ < error_margin) return;
+
+	shift_register_ = uint8_t((shift_register_ << 1) | bit);
+	if(shift_register_ & 0x80) {
+		data_register_ = shift_register_;
+		shift_register_ = 0;
+	}
+
+	if(bit)
+		cycles_since_shift_ = Cycles(0);
+	else
+		cycles_since_shift_ -= bit_length_;
+}
+
+void IWM::set_drive(int slot, IWMDrive *drive) {
+	drives_[slot] = drive;
+	drive->set_event_delegate(this);
+	drive->set_clocking_hint_observer(this);
+}
+
+void IWM::set_component_prefers_clocking(ClockingHint::Source *component, ClockingHint::Preference clocking) {
+	const bool is_rotating = clocking != ClockingHint::Preference::None;
+
+	if(component == static_cast<ClockingHint::Source *>(drives_[0])) {
+		drive_is_rotating_[0] = is_rotating;
+	} else {
+		drive_is_rotating_[1] = is_rotating;
+	}
+}
+
+void IWM::set_activity_observer(Activity::Observer *observer) {
+	if(drives_[0]) drives_[0]->set_activity_observer(observer, "Internal Floppy", true);
+	if(drives_[1]) drives_[1]->set_activity_observer(observer, "External Floppy", true);
+}

Components/DiskII/IWM.hpp

@@ -0,0 +1,124 @@
+//
+//  IWM.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 05/05/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef IWM_hpp
+#define IWM_hpp
+
+#include "../../Activity/Observer.hpp"
+
+#include "../../ClockReceiver/ClockReceiver.hpp"
+#include "../../ClockReceiver/ClockingHintSource.hpp"
+
+#include "../../Storage/Disk/Drive.hpp"
+
+#include <cstdint>
+
+namespace Apple {
+
+/*!
+	Defines the drive interface used by the IWM, derived from the external pinout as
+	per e.g. https://old.pinouts.ru/HD/MacExtDrive_pinout.shtml
+
+	These are subclassed of Storage::Disk::Drive, so accept any disk the emulator supports,
+	and provide the usual read/write interface for on-disk data.
+*/
+struct IWMDrive: public Storage::Disk::Drive {
+	IWMDrive(int input_clock_rate, int number_of_heads) : Storage::Disk::Drive(input_clock_rate, number_of_heads) {}
+
+	enum Line: int {
+		CA0		= 1 << 0,
+		CA1		= 1 << 1,
+		CA2		= 1 << 2,
+		LSTRB	= 1 << 3,
+		SEL		= 1 << 4,
+	};
+
+	virtual void set_enabled(bool) = 0;
+	virtual void set_control_lines(int) = 0;
+	virtual bool read() = 0;
+};
+
+class IWM:
+	public Storage::Disk::Drive::EventDelegate,
+	public ClockingHint::Observer {
+	public:
+		IWM(int clock_rate);
+
+		/// Sets the current external value of the data bus.
+		void write(int address, uint8_t value);
+
+		/*!
+			Submits an access to address @c address.
+
+			@returns The 8-bit value loaded to the data bus by the IWM.
+		*/
+		uint8_t read(int address);
+
+		/*!
+			Sets the current input of the IWM's SEL line.
+		*/
+		void set_select(bool enabled);
+
+		/// Advances the controller by @c cycles.
+		void run_for(const Cycles cycles);
+
+		/// Connects a drive to the IWM.
+		void set_drive(int slot, IWMDrive *drive);
+
+		/// Registers the currently-connected drives as @c Activity::Sources ;
+		/// the first will be declared 'Internal', the second 'External'.
+		void set_activity_observer(Activity::Observer *observer);
+
+	private:
+		// Storage::Disk::Drive::EventDelegate.
+		void process_event(const Storage::Disk::Drive::Event &event) override;
+
+		const int clock_rate_;
+
+		uint8_t data_register_ = 0;
+		uint8_t mode_ = 0;
+		bool read_write_ready_ = true;
+		bool write_overran_ = false;
+
+		int state_ = 0;
+
+		int active_drive_ = 0;
+		IWMDrive *drives_[2] = {nullptr, nullptr};
+		bool drive_is_rotating_[2] = {false, false};
+
+		void set_component_prefers_clocking(ClockingHint::Source *component, ClockingHint::Preference clocking) override;
+
+		Cycles cycles_until_disable_;
+		uint8_t write_handshake_ = 0x80;
+
+		void access(int address);
+
+		uint8_t shift_register_ = 0;
+		uint8_t next_output_ = 0;
+		int output_bits_remaining_ = 0;
+
+		void propose_shift(uint8_t bit);
+		Cycles cycles_since_shift_;
+		Cycles bit_length_ = Cycles(16);
+
+		void push_drive_state();
+
+		enum class ShiftMode {
+			Reading,
+			Writing,
+			CheckingWriteProtect
+		} shift_mode_;
+
+		uint8_t sense();
+		void select_shift_mode();
+};
+
+
+}
+
+#endif /* IWM_hpp */

Components/DiskII/MacintoshDoubleDensityDrive.cpp

@@ -0,0 +1,181 @@
+//
+//  MacintoshDoubleDensityDrive.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 10/07/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "MacintoshDoubleDensityDrive.hpp"
+
+/*
+	Sources used pervasively:
+
+	http://members.iinet.net.au/~kalandi/apple/AUG/1991/11%20NOV.DEC/DISK.STUFF.html
+	Apple Guide to the Macintosh Family Hardware
+	Inside Macintosh III
+*/
+
+using namespace Apple::Macintosh;
+
+DoubleDensityDrive::DoubleDensityDrive(int input_clock_rate, bool is_800k) :
+	IWMDrive(input_clock_rate, is_800k ? 2 : 1),	// Only 800kb drives are double sided.
+	is_800k_(is_800k) {
+	// Start with a valid rotation speed.
+	if(is_800k) {
+		Drive::set_rotation_speed(393.3807f);
+	}
+}
+
+// MARK: - Speed Selection
+
+void DoubleDensityDrive::did_step(Storage::Disk::HeadPosition to_position) {
+//	printf("At track %d\n", to_position.as_int());
+	// The 800kb drive automatically selects rotation speed as a function of
+	// head position; the 400kb drive doesn't do so.
+	if(is_800k_) {
+		/*
+			Numbers below cribbed from the Kryoflux forums; specifically:
+			https://forum.kryoflux.com/viewtopic.php?t=1090
+
+			They can almost be worked out algorithmically, since the point is to
+			produce an almost-constant value for speed*(number of sectors), and:
+
+			393.3807 * 12 = 4720.5684
+			429.1723 * 11 = 4720.895421
+			472.1435 * 10 = 4721.435
+			524.5672 * 9 = 4721.1048
+			590.1098 * 8 = 4720.8784
+
+			So 4721 / (number of sectors per track in zone) would give essentially
+			the same results.
+		*/
+		const int zone = to_position.as_int() >> 4;
+		switch(zone) {
+			case 0:		Drive::set_rotation_speed(393.3807f);	break;
+			case 1:		Drive::set_rotation_speed(429.1723f);	break;
+			case 2:		Drive::set_rotation_speed(472.1435f);	break;
+			case 3:		Drive::set_rotation_speed(524.5672f);	break;
+			default:	Drive::set_rotation_speed(590.1098f);	break;
+		}
+	}
+}
+
+void DoubleDensityDrive::set_rotation_speed(float revolutions_per_minute) {
+	if(!is_800k_) {
+		// Don't allow drive speeds to drop below 10 RPM, as a temporary sop
+		// to sanity.
+		Drive::set_rotation_speed(std::max(10.0f, revolutions_per_minute));
+	}
+}
+
+// MARK: - Control input/output.
+
+void DoubleDensityDrive::set_enabled(bool enabled) {
+	// Disabling a drive also stops its motor.
+	if(!enabled) set_motor_on(false);
+}
+
+void DoubleDensityDrive::set_control_lines(int lines) {
+	const auto old_state = control_state_;
+	control_state_ = lines;
+
+	// Catch low-to-high LSTRB transitions.
+	if((old_state ^ control_state_) & control_state_ & Line::LSTRB) {
+		switch(control_state_ & (Line::CA2 | Line::CA1 | Line::CA0 | Line::SEL)) {
+			default:
+			break;
+
+			case 0:						// Set step direction — CA2 set => step outward.
+			case Line::CA2:
+				step_direction_ = (control_state_ & Line::CA2) ? -1 : 1;
+			break;
+
+			case Line::CA1:				// Set drive motor — CA2 set => motor off.
+			case Line::CA1|Line::CA2:
+				set_motor_on(!(control_state_ & Line::CA2));
+			break;
+
+			case Line::CA0:				// Initiate a step.
+				step(Storage::Disk::HeadPosition(step_direction_));
+			break;
+
+			case Line::SEL|Line::CA2:	// Reset new disk flag.
+				has_new_disk_ = false;
+			break;
+
+			case Line::CA2 | Line::CA1 | Line::CA0:	// Eject the disk.
+				set_disk(nullptr);
+			break;
+		}
+	}
+}
+
+bool DoubleDensityDrive::read() {
+	switch(control_state_ & (CA2 | CA1 | CA0 | SEL)) {
+		default:
+		return false;
+
+		case 0:					// Head step direction.
+								// (0 = inward)
+		return step_direction_ <= 0;
+
+		case SEL:				// Disk in place.
+								// (0 = disk present)
+		return !has_disk();
+
+		case CA0:				// Disk head step completed.
+								// (0 = still stepping)
+		return true;	// TODO: stepping delay. But at the main Drive level.
+
+		case CA0|SEL:			// Disk locked.
+								// (0 = write protected)
+		return !get_is_read_only();
+
+		case CA1:				// Disk motor running.
+								// (0 = motor on)
+		return !get_motor_on();
+
+		case CA1|SEL:			// Head at track 0.
+								// (0 = at track 0)
+								// "This bit becomes valid beginning 12 msec after the step that places the head at track 0."
+		return !get_is_track_zero();
+
+		case CA1|CA0:			// Disk has been ejected.
+								// (0 = user has ejected disk)
+		return !has_new_disk_;
+
+		case CA1|CA0|SEL:		// Tachometer.
+								// (arbitrary)
+		return get_tachometer();
+
+		case CA2:				// Read data, lower head.
+			set_head(0);
+		return false;
+
+		case CA2|SEL:			// Read data, upper head.
+			set_head(1);
+		return false;
+
+		case CA2|CA1:			// Single- or double-sided drive.
+								// (0 = single sided)
+		return get_head_count() != 1;
+
+		case CA2|CA1|CA0:		// "Present/HD" (per the Mac Plus ROM)
+								// (0 = ??HD??)
+								//
+								// Alternative explanation: "Disk ready for reading?"
+								// (0 = ready)
+		return false;
+
+		case CA2|CA1|CA0|SEL:	// Drive installed.
+								// (0 = present, 1 = missing)
+								//
+								// TODO: why do I need to return this the wrong way around for the Mac Plus?
+		return true;
+	}
+}
+
+void DoubleDensityDrive::did_set_disk() {
+	has_new_disk_ = true;
+}

Components/DiskII/MacintoshDoubleDensityDrive.hpp

@@ -0,0 +1,53 @@
+//
+//  MacintoshDoubleDensityDrive.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 10/07/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef MacintoshDoubleDensityDrive_hpp
+#define MacintoshDoubleDensityDrive_hpp
+
+#include "IWM.hpp"
+
+namespace Apple {
+namespace Macintosh {
+
+class DoubleDensityDrive: public IWMDrive {
+	public:
+		DoubleDensityDrive(int input_clock_rate, bool is_800k);
+
+		/*!
+			@returns @c true if this is an 800kb drive; @c false otherwise.
+		*/
+		bool is_800k() {
+			return is_800k_;
+		}
+
+		/*!
+			Sets the current rotation speed of this drive only if it is a 400kb drive.
+			800kb drives select their own rotation speed based on head position,
+			and ignore this input.
+		*/
+		void set_rotation_speed(float revolutions_per_minute);
+
+		void set_enabled(bool) override;
+		void set_control_lines(int) override;
+		bool read() override;
+
+	private:
+		// To receive the proper notifications from Storage::Disk::Drive.
+		void did_step(Storage::Disk::HeadPosition to_position) override;
+		void did_set_disk() override;
+
+		const bool is_800k_;
+		bool has_new_disk_ = false;
+		int control_state_ = 0;
+		int step_direction_ = 1;
+};
+
+}
+}
+
+#endif /* MacintoshDoubleDensityDrive_hpp */

Components/SN76489/SN76489.cpp

@@ -48,7 +48,7 @@ void SN76489::set_sample_volume_range(std::int16_t range) {
 	evaluate_output_volume();
 }
 
-void SN76489::set_register(uint8_t value) {
+void SN76489::write(uint8_t value) {
 	task_queue_.defer([value, this] () {
 		if(value & 0x80) {
 			active_register_ = value;

Components/SN76489/SN76489.hpp

@@ -26,7 +26,7 @@ class SN76489: public Outputs::Speaker::SampleSource {
 		SN76489(Personality personality, Concurrency::DeferringAsyncTaskQueue &task_queue, int additional_divider = 1);
 
 		/// Writes a new value to the SN76489.
-		void set_register(uint8_t value);
+		void write(uint8_t value);
 
 		// As per SampleSource.
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);

Components/Serial/Line.cpp

@@ -0,0 +1,140 @@
+//
+//  SerialPort.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 12/10/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "Line.hpp"
+
+using namespace Serial;
+
+void Line::set_writer_clock_rate(HalfCycles clock_rate) {
+	clock_rate_ = clock_rate;
+}
+
+void Line::advance_writer(HalfCycles cycles) {
+	if(cycles == HalfCycles(0)) return;
+
+	const auto integral_cycles = cycles.as_integral();
+	remaining_delays_ = std::max(remaining_delays_ - integral_cycles, Cycles::IntType(0));
+	if(events_.empty()) {
+		write_cycles_since_delegate_call_ += integral_cycles;
+		if(transmission_extra_) {
+			transmission_extra_ -= integral_cycles;
+			if(transmission_extra_ <= 0) {
+				transmission_extra_ = 0;
+				update_delegate(level_);
+			}
+		}
+	} else {
+		while(!events_.empty()) {
+			if(events_.front().delay <= integral_cycles) {
+				cycles -= events_.front().delay;
+				write_cycles_since_delegate_call_ += events_.front().delay;
+				const auto old_level = level_;
+
+				auto iterator = events_.begin() + 1;
+				while(iterator != events_.end() && iterator->type != Event::Delay) {
+					level_ = iterator->type == Event::SetHigh;
+					++iterator;
+				}
+				events_.erase(events_.begin(), iterator);
+
+				if(old_level != level_) {
+					update_delegate(old_level);
+				}
+
+				// Book enough extra time for the read delegate to be posted
+				// the final bit if one is attached.
+				if(events_.empty()) {
+					transmission_extra_ = minimum_write_cycles_for_read_delegate_bit();
+				}
+			} else {
+				events_.front().delay -= integral_cycles;
+				write_cycles_since_delegate_call_ += integral_cycles;
+				break;
+			}
+		}
+	}
+}
+
+void Line::write(bool level) {
+	if(!events_.empty()) {
+		events_.emplace_back();
+		events_.back().type = level ? Event::SetHigh : Event::SetLow;
+	} else {
+		level_ = level;
+		transmission_extra_ = minimum_write_cycles_for_read_delegate_bit();
+	}
+}
+
+void Line::write(HalfCycles cycles, int count, int levels) {
+	remaining_delays_ += count * cycles.as_integral();
+
+	auto event = events_.size();
+	events_.resize(events_.size() + size_t(count)*2);
+	while(count--) {
+		events_[event].type = Event::Delay;
+		events_[event].delay = int(cycles.as_integral());
+		events_[event+1].type = (levels&1) ? Event::SetHigh : Event::SetLow;
+		levels >>= 1;
+		event += 2;
+	}
+}
+
+void Line::reset_writing() {
+	remaining_delays_ = 0;
+	events_.clear();
+}
+
+bool Line::read() {
+	return level_;
+}
+
+void Line::set_read_delegate(ReadDelegate *delegate, Storage::Time bit_length) {
+	read_delegate_ = delegate;
+	read_delegate_bit_length_ = bit_length;
+	read_delegate_bit_length_.simplify();
+	write_cycles_since_delegate_call_ = 0;
+}
+
+void Line::update_delegate(bool level) {
+	// Exit early if there's no delegate, or if the delegate is waiting for
+	// zero and this isn't zero.
+	if(!read_delegate_) return;
+
+	const int cycles_to_forward = write_cycles_since_delegate_call_;
+	write_cycles_since_delegate_call_ = 0;
+	if(level && read_delegate_phase_ == ReadDelegatePhase::WaitingForZero) return;
+
+	// Deal with a transition out of waiting-for-zero mode by seeding time left
+	// in bit at half a bit.
+	if(read_delegate_phase_ == ReadDelegatePhase::WaitingForZero) {
+		time_left_in_bit_ = read_delegate_bit_length_;
+		time_left_in_bit_.clock_rate <<= 1;
+		read_delegate_phase_ = ReadDelegatePhase::Serialising;
+	}
+
+	// Forward as many bits as occur.
+	Storage::Time time_left(cycles_to_forward, int(clock_rate_.as_integral()));
+	const int bit = level ? 1 : 0;
+	int bits = 0;
+	while(time_left >= time_left_in_bit_) {
+		++bits;
+		if(!read_delegate_->serial_line_did_produce_bit(this, bit)) {
+			read_delegate_phase_ = ReadDelegatePhase::WaitingForZero;
+			if(bit) return;
+		}
+
+		time_left -= time_left_in_bit_;
+		time_left_in_bit_ = read_delegate_bit_length_;
+	}
+	time_left_in_bit_ -= time_left;
+}
+
+Cycles::IntType Line::minimum_write_cycles_for_read_delegate_bit() {
+	if(!read_delegate_) return 0;
+	return 1 + (read_delegate_bit_length_ * static_cast<unsigned int>(clock_rate_.as_integral())).get<int>();
+}

Components/Serial/Line.hpp

@@ -0,0 +1,112 @@
+//
+//  SerialPort.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 12/10/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef SerialPort_hpp
+#define SerialPort_hpp
+
+#include <vector>
+#include "../../Storage/Storage.hpp"
+#include "../../ClockReceiver/ClockReceiver.hpp"
+#include "../../ClockReceiver/ForceInline.hpp"
+
+namespace Serial {
+
+/*!
+	@c Line connects a single reader and a single writer, allowing timestamped events to be
+	published and consumed, potentially with a clock conversion in between. It allows line
+	levels to be written and read in larger collections.
+
+	It is assumed that the owner of the reader and writer will ensure that the reader will never
+	get ahead of the writer. If the writer posts events behind the reader they will simply be
+	given instanteous effect.
+*/
+class Line {
+	public:
+		void set_writer_clock_rate(HalfCycles clock_rate);
+
+		/// Advances the read position by @c cycles relative to the writer's
+		/// clock rate.
+		void advance_writer(HalfCycles cycles);
+
+		/// Sets the line to @c level.
+		void write(bool level);
+
+		/// Enqueues @c count level changes, the first occurring immediately
+		/// after the final event currently posted and each subsequent event
+		/// occurring @c cycles after the previous. An additional gap of @c cycles
+		/// is scheduled after the final output. The levels to output are
+		/// taken from @c levels which is read from lsb to msb. @c cycles is
+		/// relative to the writer's clock rate.
+		void write(HalfCycles cycles, int count, int levels);
+
+		/// @returns the number of cycles until currently enqueued write data is exhausted.
+		forceinline HalfCycles write_data_time_remaining() const {
+			return HalfCycles(remaining_delays_);
+		}
+
+		/// @returns the number of cycles left until it is guaranteed that a passive reader
+		/// has received all currently-enqueued bits.
+		forceinline HalfCycles transmission_data_time_remaining() const {
+			return HalfCycles(remaining_delays_ + transmission_extra_);
+		}
+
+		/// Eliminates all future write states, leaving the output at whatever it is now.
+		void reset_writing();
+
+		/// @returns The instantaneous level of this line.
+		bool read();
+
+		struct ReadDelegate {
+			virtual bool serial_line_did_produce_bit(Line *line, int bit) = 0;
+		};
+		/*!
+			Sets a read delegate, which will receive samples of the output level every
+			@c bit_lengths of a second apart subject to a state machine:
+
+				* initially no bits will be delivered;
+				* when a zero level is first detected, the line will wait half a bit's length, then start
+				sampling at single-bit intervals, passing each bit to the delegate while it returns @c true;
+				* as soon as the delegate returns @c false, the line will return to the initial state.
+		*/
+		void set_read_delegate(ReadDelegate *delegate, Storage::Time bit_length);
+
+	private:
+		struct Event {
+			enum Type {
+				Delay, SetHigh, SetLow
+			} type;
+			int delay;
+		};
+		std::vector<Event> events_;
+		HalfCycles::IntType remaining_delays_ = 0;
+		HalfCycles::IntType transmission_extra_ = 0;
+		bool level_ = true;
+		HalfCycles clock_rate_ = 0;
+
+		ReadDelegate *read_delegate_ = nullptr;
+		Storage::Time read_delegate_bit_length_, time_left_in_bit_;
+		int write_cycles_since_delegate_call_ = 0;
+		enum class ReadDelegatePhase {
+			WaitingForZero,
+			Serialising
+		} read_delegate_phase_ = ReadDelegatePhase::WaitingForZero;
+
+		void update_delegate(bool level);
+		HalfCycles::IntType minimum_write_cycles_for_read_delegate_bit();
+};
+
+/*!
+	Defines an RS-232-esque srial port.
+*/
+class Port {
+	public:
+};
+
+}
+
+#endif /* SerialPort_hpp */

Concurrency/AsyncTaskQueue.cpp

@@ -18,7 +18,7 @@ AsyncTaskQueue::AsyncTaskQueue()
 #ifdef __APPLE__
 	serial_dispatch_queue_ = dispatch_queue_create("com.thomasharte.clocksignal.asyntaskqueue", DISPATCH_QUEUE_SERIAL);
 #else
-	thread_.reset(new std::thread([this]() {
+	thread_ = std::make_unique<std::thread>([this]() {
 		while(!should_destruct_) {
 			std::function<void(void)> next_function;
 
@@ -39,7 +39,7 @@ AsyncTaskQueue::AsyncTaskQueue()
 				processing_condition_.wait(lock);
 			}
 		}
-	}));
+	});
 #endif
 }
 
@@ -70,8 +70,8 @@ void AsyncTaskQueue::flush() {
 #ifdef __APPLE__
 	dispatch_sync(serial_dispatch_queue_, ^{});
 #else
-	std::shared_ptr<std::mutex> flush_mutex(new std::mutex);
-	std::shared_ptr<std::condition_variable> flush_condition(new std::condition_variable);
+	auto flush_mutex = std::make_shared<std::mutex>();
+	auto flush_condition = std::make_shared<std::condition_variable>();
 	std::unique_lock<std::mutex> lock(*flush_mutex);
 	enqueue([=] () {
 		std::unique_lock<std::mutex> inner_lock(*flush_mutex);
@@ -88,7 +88,7 @@ DeferringAsyncTaskQueue::~DeferringAsyncTaskQueue() {
 
 void DeferringAsyncTaskQueue::defer(std::function<void(void)> function) {
 	if(!deferred_tasks_) {
-		deferred_tasks_.reset(new std::list<std::function<void(void)>>);
+		deferred_tasks_ = std::make_shared<std::list<std::function<void(void)>>>();
 	}
 	deferred_tasks_->push_back(function);
 }

Configurable/Configurable.cpp

@@ -19,7 +19,7 @@ ListSelection *ListSelection::list_selection() {
 }
 
 BooleanSelection *ListSelection::boolean_selection() {
-	return new BooleanSelection(value != "no" && value != "n");
+	return new BooleanSelection(value != "no" && value != "n" && value != "false" && value != "f");
 }
 
 BooleanSelection *BooleanSelection::boolean_selection() {

Configurable/StandardOptions.cpp

@@ -14,16 +14,16 @@ namespace {
 	Appends a Boolean selection of @c selection for option @c name to @c selection_set.
 */
 void append_bool(Configurable::SelectionSet &selection_set, const std::string &name, bool selection) {
-	selection_set[name] = std::unique_ptr<Configurable::Selection>(new Configurable::BooleanSelection(selection));
+	selection_set[name] = std::make_unique<Configurable::BooleanSelection>(selection);
 }
 
 /*!
 	Enquires for a Boolean selection for option @c name from @c selections_by_option, storing it to @c result if found.
 */
 bool get_bool(const Configurable::SelectionSet &selections_by_option, const std::string &name, bool &result) {
-	auto quickload = Configurable::selection<Configurable::BooleanSelection>(selections_by_option, "quickload");
-	if(!quickload) return false;
-	result = quickload->value;
+	auto selection = Configurable::selection<Configurable::BooleanSelection>(selections_by_option, name);
+	if(!selection) return false;
+	result = selection->value;
 	return true;
 }
 
@@ -33,14 +33,16 @@ bool get_bool(const Configurable::SelectionSet &selections_by_option, const std:
 std::vector<std::unique_ptr<Configurable::Option>> Configurable::standard_options(Configurable::StandardOptions mask) {
 	std::vector<std::unique_ptr<Configurable::Option>> options;
 	if(mask & QuickLoadTape)				options.emplace_back(new Configurable::BooleanOption("Load Tapes Quickly", "quickload"));
-	if(mask & (DisplayRGB | DisplayComposite | DisplaySVideo)) {
+	if(mask & (DisplayRGB | DisplayCompositeColour | DisplayCompositeMonochrome | DisplaySVideo)) {
 		std::vector<std::string> display_options;
-		if(mask & DisplayComposite)	display_options.emplace_back("composite");
-		if(mask & DisplaySVideo) 	display_options.emplace_back("svideo");
-		if(mask & DisplayRGB) 		display_options.emplace_back("rgb");
+		if(mask & DisplayCompositeColour)		display_options.emplace_back("composite");
+		if(mask & DisplayCompositeMonochrome)	display_options.emplace_back("composite-mono");
+		if(mask & DisplaySVideo)				display_options.emplace_back("svideo");
+		if(mask & DisplayRGB)					display_options.emplace_back("rgb");
 		options.emplace_back(new Configurable::ListOption("Display", "display", display_options));
 	}
 	if(mask & AutomaticTapeMotorControl)	options.emplace_back(new Configurable::BooleanOption("Automatic Tape Motor Control", "autotapemotor"));
+	if(mask & QuickBoot)					options.emplace_back(new Configurable::BooleanOption("Boot Quickly", "quickboot"));
 	return options;
 }
 
@@ -57,11 +59,16 @@ void Configurable::append_display_selection(Configurable::SelectionSet &selectio
 	std::string string_selection;
 	switch(selection) {
 		default:
-		case Display::RGB:			string_selection = "rgb";		break;
-		case Display::SVideo:		string_selection = "svideo";	break;
-		case Display::Composite:	string_selection = "composite";	break;
+		case Display::RGB:					string_selection = "rgb";				break;
+		case Display::SVideo:				string_selection = "svideo";			break;
+		case Display::CompositeMonochrome:	string_selection = "composite-mono";	break;
+		case Display::CompositeColour:		string_selection = "composite";			break;
 	}
-	selection_set["display"] = std::unique_ptr<Configurable::Selection>(new Configurable::ListSelection(string_selection));
+	selection_set["display"] = std::make_unique<Configurable::ListSelection>(string_selection);
+}
+
+void Configurable::append_quick_boot_selection(Configurable::SelectionSet &selection_set, bool selection) {
+	append_bool(selection_set, "quickboot", selection);
 }
 
 // MARK: - Selection parsers
@@ -85,9 +92,17 @@ bool Configurable::get_display(const Configurable::SelectionSet &selections_by_o
 			return true;
 		}
 		if(display->value == "composite") {
-			result = Configurable::Display::Composite;
+			result = Configurable::Display::CompositeColour;
+			return true;
+		}
+		if(display->value == "composite-mono") {
+			result = Configurable::Display::CompositeMonochrome;
 			return true;
 		}
 	}
 	return false;
 }
+
+bool Configurable::get_quick_boot(const Configurable::SelectionSet &selections_by_option, bool &result) {
+	return get_bool(selections_by_option, "quickboot", result);
+}

Configurable/StandardOptions.hpp

@@ -16,15 +16,18 @@ namespace Configurable {
 enum StandardOptions {
 	DisplayRGB					= (1 << 0),
 	DisplaySVideo				= (1 << 1),
-	DisplayComposite			= (1 << 2),
-	QuickLoadTape				= (1 << 3),
-	AutomaticTapeMotorControl	= (1 << 4)
+	DisplayCompositeColour		= (1 << 2),
+	DisplayCompositeMonochrome	= (1 << 3),
+	QuickLoadTape				= (1 << 4),
+	AutomaticTapeMotorControl	= (1 << 5),
+	QuickBoot					= (1 << 6),
 };
 
 enum class Display {
 	RGB,
 	SVideo,
-	Composite
+	CompositeColour,
+	CompositeMonochrome
 };
 
 /*!
@@ -47,6 +50,11 @@ void append_automatic_tape_motor_control_selection(SelectionSet &selection_set,
 */
 void append_display_selection(SelectionSet &selection_set, Display selection);
 
+/*!
+	Appends to @c selection_set a selection of @c selection for QuickBoot.
+*/
+void append_quick_boot_selection(SelectionSet &selection_set, bool selection);
+
 /*!
 	Attempts to discern a QuickLoadTape selection from @c selections_by_option.
  
@@ -74,6 +82,15 @@ bool get_automatic_tape_motor_control_selection(const SelectionSet &selections_b
 */
 bool get_display(const SelectionSet &selections_by_option, Display &result);
 
+/*!
+	Attempts to QuickBoot a QuickLoadTape selection from @c selections_by_option.
+
+	@param selections_by_option The user selections.
+	@param result The location to which the selection will be stored if found.
+	@returns @c true if a selection is found; @c false otherwise.
+*/
+bool get_quick_boot(const SelectionSet &selections_by_option, bool &result);
+
 }
 
 #endif /* StandardOptions_hpp */

Inputs/Joystick.hpp

@@ -185,7 +185,7 @@ class ConcreteJoystick: public Joystick {
 			// convenient hard-coded values. TODO: make these a function of time.
 			using Type = Joystick::Input::Type;
 			switch(input.type) {
-				default: 			did_set_input(input, is_active ? 1.0f : 0.0f);													break;
+				default:			did_set_input(input, is_active ? 1.0f : 0.0f);													break;
 				case Type::Left:	did_set_input(Input(Type::Horizontal, input.info.control.index), is_active ? 0.1f : 0.5f);		break;
 				case Type::Right:	did_set_input(Input(Type::Horizontal, input.info.control.index), is_active ? 0.9f : 0.5f);		break;
 				case Type::Up:		did_set_input(Input(Type::Vertical, input.info.control.index), is_active ? 0.1f : 0.5f);		break;
@@ -203,7 +203,7 @@ class ConcreteJoystick: public Joystick {
 			// Otherwise apply a threshold test to convert to digital, with remapping from axes to digital inputs.
 			using Type = Joystick::Input::Type;
 			switch(input.type) {
-				default: 			did_set_input(input, value > 0.5f);											break;
+				default:			did_set_input(input, value > 0.5f);											break;
 				case Type::Horizontal:
 					did_set_input(Input(Type::Left, input.info.control.index), value <= 0.25f);
 					did_set_input(Input(Type::Right, input.info.control.index), value >= 0.75f);

Inputs/Keyboard.cpp

@@ -10,7 +10,14 @@
 
 using namespace Inputs;
 
-Keyboard::Keyboard() {}
+Keyboard::Keyboard(const std::set<Key> &essential_modifiers) : essential_modifiers_(essential_modifiers) {
+	for(int k = 0; k < int(Key::Help); ++k) {
+		observed_keys_.insert(Key(k));
+	}
+}
+
+Keyboard::Keyboard(const std::set<Key> &observed_keys, const std::set<Key> &essential_modifiers) :
+	observed_keys_(observed_keys), essential_modifiers_(essential_modifiers), is_exclusive_(false) {}
 
 void Keyboard::set_key_pressed(Key key, char value, bool is_pressed) {
 	std::size_t key_offset = static_cast<std::size_t>(key);
@@ -22,6 +29,10 @@ void Keyboard::set_key_pressed(Key key, char value, bool is_pressed) {
 	if(delegate_) delegate_->keyboard_did_change_key(this, key, is_pressed);
 }
 
+const std::set<Inputs::Keyboard::Key> &Keyboard::get_essential_modifiers() {
+	return essential_modifiers_;
+}
+
 void Keyboard::reset_all_keys() {
 	std::fill(key_states_.begin(), key_states_.end(), false);
 	if(delegate_) delegate_->reset_all_keys(this);
@@ -36,3 +47,11 @@ bool Keyboard::get_key_state(Key key) {
 	if(key_offset >= key_states_.size()) return false;
 	return key_states_[key_offset];
 }
+
+const std::set<Keyboard::Key> &Keyboard::observed_keys() {
+	return observed_keys_;
+}
+
+bool Keyboard::is_exclusive() {
+	return is_exclusive_;
+}

Inputs/Keyboard.hpp

@@ -6,10 +6,11 @@
 //  Copyright 2017 Thomas Harte. All rights reserved.
 //
 
-#ifndef Keyboard_hpp
-#define Keyboard_hpp
+#ifndef Inputs_Keyboard_hpp
+#define Inputs_Keyboard_hpp
 
 #include <vector>
+#include <set>
 
 namespace Inputs {
 
@@ -20,29 +21,51 @@ namespace Inputs {
 */
 class Keyboard {
 	public:
-		Keyboard();
-
 		enum class Key {
 			Escape, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12, PrintScreen, ScrollLock, Pause,
-			BackTick, k1, k2, k3, k4, k5, k6, k7, k8, k9, k0, Hyphen, Equals, BackSpace,
-			Tab, Q, W, E, R, T, Y, U, I, O, P, OpenSquareBracket, CloseSquareBracket, BackSlash,
+			BackTick, k1, k2, k3, k4, k5, k6, k7, k8, k9, k0, Hyphen, Equals, Backspace,
+			Tab, Q, W, E, R, T, Y, U, I, O, P, OpenSquareBracket, CloseSquareBracket, Backslash,
 			CapsLock, A, S, D, F, G, H, J, K, L, Semicolon, Quote, Hash, Enter,
 			LeftShift, Z, X, C, V, B, N, M, Comma, FullStop, ForwardSlash, RightShift,
 			LeftControl, LeftOption, LeftMeta, Space, RightMeta, RightOption, RightControl,
 			Left, Right, Up, Down,
 			Insert, Home, PageUp, Delete, End, PageDown,
-			NumLock, KeyPadSlash, KeyPadAsterisk, KeyPadDelete,
-			KeyPad7, KeyPad8, KeyPad9, KeyPadPlus,
-			KeyPad4, KeyPad5, KeyPad6, KeyPadMinus,
-			KeyPad1, KeyPad2, KeyPad3, KeyPadEnter,
-			KeyPad0, KeyPadDecimalPoint, KeyPadEquals,
+			NumLock, KeypadSlash, KeypadAsterisk, KeypadDelete,
+			Keypad7, Keypad8, Keypad9, KeypadPlus,
+			Keypad4, Keypad5, Keypad6, KeypadMinus,
+			Keypad1, Keypad2, Keypad3, KeypadEnter,
+			Keypad0, KeypadDecimalPoint, KeypadEquals,
 			Help
 		};
 
+		/// Constructs a Keyboard that declares itself to observe all keys.
+		Keyboard(const std::set<Key> &essential_modifiers = {});
+
+		/// Constructs a Keyboard that declares itself to observe only members of @c observed_keys.
+		Keyboard(const std::set<Key> &observed_keys, const std::set<Key> &essential_modifiers);
+
 		// Host interface.
 		virtual void set_key_pressed(Key key, char value, bool is_pressed);
 		virtual void reset_all_keys();
 
+		/// @returns a set of all Keys that this keyboard responds to.
+		virtual const std::set<Key> &observed_keys();
+
+		/// @returns the list of modifiers that this keyboard considers 'essential' (i.e. both mapped and highly used).
+		virtual const std::set<Inputs::Keyboard::Key> &get_essential_modifiers();
+
+		/*!
+			@returns @c true if this keyboard, on its original machine, looked
+			like a complete keyboard — i.e. if a user would expect this keyboard
+			to be the only thing a real keyboard maps to.
+
+			So this would be true of something like the Amstrad CPC, which has a full
+			keyboard, but it would be false of something like the Sega Master System
+			which has some buttons that you'd expect an emulator to map to its host
+			keyboard but which does not offer a full keyboard.
+		*/
+		virtual bool is_exclusive();
+
 		// Delegate interface.
 		struct Delegate {
 			virtual void keyboard_did_change_key(Keyboard *keyboard, Key key, bool is_pressed) = 0;
@@ -52,10 +75,13 @@ class Keyboard {
 		bool get_key_state(Key key);
 
 	private:
+		std::set<Key> observed_keys_;
+		std::set<Key> essential_modifiers_;
 		std::vector<bool> key_states_;
 		Delegate *delegate_ = nullptr;
+		bool is_exclusive_ = true;
 };
 
 }
 
-#endif /* Keyboard_hpp */
+#endif /* Inputs_Keyboard_hpp */

Inputs/Mouse.hpp

@@ -0,0 +1,47 @@
+//
+//  Mouse.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 11/06/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef Mouse_h
+#define Mouse_h
+
+namespace Inputs {
+
+/*!
+	Models a classic-era mouse: something that provides 2d relative motion plus
+	some quantity of buttons.
+*/
+class Mouse {
+	public:
+		/*!
+			Indicates a movement of the mouse.
+		*/
+		virtual void move(int x, int y) {}
+
+		/*!
+			@returns the number of buttons on this mouse.
+		*/
+		virtual int get_number_of_buttons() {
+			return 1;
+		}
+
+		/*!
+			Indicates that button @c index is now either pressed or unpressed.
+			The intention is that @c index be semantic, not positional:
+			0 for the primary button, 1 for the secondary, 2 for the tertiary, etc.
+		*/
+		virtual void set_button_pressed(int index, bool is_pressed) {}
+
+		/*!
+			Releases all depressed buttons.
+		*/
+		virtual void reset_all_buttons() {}
+};
+
+}
+
+#endif /* Mouse_h */

Inputs/QuadratureMouse/QuadratureMouse.hpp

@@ -0,0 +1,123 @@
+//
+//  QuadratureMouse.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 11/06/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef QuadratureMouse_hpp
+#define QuadratureMouse_hpp
+
+#include "../Mouse.hpp"
+#include <atomic>
+
+namespace Inputs {
+
+/*!
+	Provides a simple implementation of a Mouse, designed for simple
+	thread-safe feeding to a machine that accepts quadrature-encoded input.
+
+	TEMPORARY SIMPLIFICATION: it is assumed that the caller will be interested
+	in observing a signal that dictates velocity, sampling the other to
+	obtain direction only on transitions in the velocity signal.
+
+	Or, more concretely, of the two channels per axis, one is accurate only when
+	the other transitions. Hence the discussion of 'primary' and 'secondary'
+	channels below. This is intended to be fixed.
+*/
+class QuadratureMouse: public Mouse {
+	public:
+		QuadratureMouse(int number_of_buttons) :
+			number_of_buttons_(number_of_buttons) {}
+
+		/*
+			Inputs, to satisfy the Mouse interface.
+		*/
+		void move(int x, int y) override {
+			// Accumulate all provided motion.
+			axes_[0] += x;
+			axes_[1] += y;
+		}
+
+		int get_number_of_buttons() override {
+			return number_of_buttons_;
+		}
+
+		void set_button_pressed(int index, bool is_pressed) override {
+			if(is_pressed)
+				button_flags_ |= (1 << index);
+			else
+				button_flags_ &= ~(1 << index);
+		}
+
+		void reset_all_buttons() override {
+			button_flags_ = 0;
+		}
+
+		/*
+			Outputs.
+		*/
+
+		/*!
+			Applies a single step from the current accumulated mouse movement, which
+			might involve the mouse moving right, or left, or not at all.
+		*/
+		void prepare_step() {
+			for(int axis = 0; axis < 2; ++axis) {
+				// Do nothing if there's no motion to communicate.
+				const int axis_value = axes_[axis];
+				if(!axis_value) continue;
+
+				// Toggle the primary channel and set the secondary for
+				// negative motion. At present the y axis signals the
+				// secondary channel the opposite way around from the
+				// primary.
+				primaries_[axis] ^= 1;
+				secondaries_[axis] = primaries_[axis] ^ axis;
+				if(axis_value > 0) {
+					-- axes_[axis];
+					secondaries_[axis] ^= 1;	// Switch to positive motion.
+				} else {
+					++ axes_[axis];
+				}
+			}
+		}
+
+		/*!
+			@returns the two quadrature channels — bit 0 is the 'primary' channel
+				(i.e. the one that can be monitored to observe velocity) and
+				bit 1 is the 'secondary' (i.e. that which can be queried to
+				observe direction).
+		*/
+		int get_channel(int axis) {
+			return primaries_[axis] | (secondaries_[axis] << 1);
+		}
+
+		/*!
+			@returns a bit mask of the currently pressed buttons.
+		*/
+		int get_button_mask() {
+			return button_flags_;
+		}
+
+		/*!
+			@returns @c true if any mouse motion is waiting to be communicated;
+				@c false otherwise.
+		*/
+		bool has_steps() {
+			return axes_[0] || axes_[1];
+		}
+
+	private:
+		int number_of_buttons_ = 0;
+		std::atomic<int> button_flags_;
+		std::atomic<int> axes_[2];
+
+		int primaries_[2] = {0, 0};
+		int secondaries_[2] = {0, 0};
+};
+
+}
+
+#endif /* QuadratureMouse_hpp */

Machines/AmstradCPC/AmstradCPC.cpp

@@ -30,6 +30,7 @@
 
 #include "../../ClockReceiver/ForceInline.hpp"
 #include "../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
+#include "../../Outputs/CRT/CRT.hpp"
 
 #include "../../Analyser/Static/AmstradCPC/Target.hpp"
 
@@ -40,7 +41,7 @@ namespace AmstradCPC {
 
 std::vector<std::unique_ptr<Configurable::Option>> get_options() {
 	return Configurable::standard_options(
-		static_cast<Configurable::StandardOptions>(Configurable::DisplayRGB | Configurable::DisplayComposite)
+		Configurable::StandardOptions(Configurable::DisplayRGB | Configurable::DisplayCompositeColour)
 	);
 }
 
@@ -123,7 +124,7 @@ class InterruptTimer {
 class AYDeferrer {
 	public:
 		/// Constructs a new AY instance and sets its clock rate.
-		AYDeferrer() : ay_(audio_queue_), speaker_(ay_) {
+		AYDeferrer() : ay_(GI::AY38910::Personality::AY38910, audio_queue_), speaker_(ay_) {
 			speaker_.set_input_rate(1000000);
 		}
 
@@ -170,11 +171,15 @@ class AYDeferrer {
 */
 class CRTCBusHandler {
 	public:
-		CRTCBusHandler(uint8_t *ram, InterruptTimer &interrupt_timer) :
+		CRTCBusHandler(const uint8_t *ram, InterruptTimer &interrupt_timer) :
+			crt_(1024, 1, Outputs::Display::Type::PAL50, Outputs::Display::InputDataType::Red2Green2Blue2),
 			ram_(ram),
 			interrupt_timer_(interrupt_timer) {
 				establish_palette_hits();
 				build_mode_table();
+				crt_.set_visible_area(Outputs::Display::Rect(0.1072f, 0.1f, 0.842105263157895f, 0.842105263157895f));
+				crt_.set_brightness(3.0f / 2.0f);	// As only the values 0, 1 and 2 will be used in each channel,
+													// whereas Red2Green2Blue2 defines a range of 0-3.
 			}
 
 		/*!
@@ -217,12 +222,12 @@ class CRTCBusHandler {
 				if(cycles_) {
 					switch(previous_output_mode_) {
 						default:
-						case OutputMode::Blank:			crt_->output_blank(cycles_ * 16);					break;
-						case OutputMode::Sync:			crt_->output_sync(cycles_ * 16);					break;
-						case OutputMode::Border:		output_border(cycles_);								break;
-						case OutputMode::ColourBurst:	crt_->output_default_colour_burst(cycles_ * 16);	break;
+						case OutputMode::Blank:			crt_.output_blank(cycles_ * 16);				break;
+						case OutputMode::Sync:			crt_.output_sync(cycles_ * 16);					break;
+						case OutputMode::Border:		output_border(cycles_);							break;
+						case OutputMode::ColourBurst:	crt_.output_default_colour_burst(cycles_ * 16);	break;
 						case OutputMode::Pixels:
-							crt_->output_data(cycles_ * 16, cycles_ * 16 / pixel_divider_);
+							crt_.output_data(cycles_ * 16, size_t(cycles_ * 16 / pixel_divider_));
 							pixel_pointer_ = pixel_data_ = nullptr;
 						break;
 					}
@@ -238,52 +243,54 @@ class CRTCBusHandler {
 			// collect some more pixels if output is ongoing
 			if(previous_output_mode_ == OutputMode::Pixels) {
 				if(!pixel_data_) {
-					pixel_pointer_ = pixel_data_ = crt_->allocate_write_area(320, 8);
+					pixel_pointer_ = pixel_data_ = crt_.begin_data(320, 8);
 				}
 				if(pixel_pointer_) {
 					// the CPC shuffles output lines as:
 					//	MA13 MA12	RA2 RA1 RA0		MA9 MA8 MA7 MA6 MA5 MA4 MA3 MA2 MA1 MA0		CCLK
 					// ... so form the real access address.
-					uint16_t address =
-						static_cast<uint16_t>(
+					const uint16_t address =
+						uint16_t(
 							((state.refresh_address & 0x3ff) << 1) |
 							((state.row_address & 0x7) << 11) |
 							((state.refresh_address & 0x3000) << 2)
 						);
 
-					// fetch two bytes and translate into pixels
+					// Fetch two bytes and translate into pixels. Guaranteed: the mode can change only at
+					// hsync, so there's no risk of pixel_pointer_ overrunning 320 output pixels without
+					// exactly reaching 320 output pixels.
 					switch(mode_) {
 						case 0:
 							reinterpret_cast<uint16_t *>(pixel_pointer_)[0] = mode0_output_[ram_[address]];
 							reinterpret_cast<uint16_t *>(pixel_pointer_)[1] = mode0_output_[ram_[address+1]];
-							pixel_pointer_ += 4;
+							pixel_pointer_ += 2 * sizeof(uint16_t);
 						break;
 
 						case 1:
 							reinterpret_cast<uint32_t *>(pixel_pointer_)[0] = mode1_output_[ram_[address]];
 							reinterpret_cast<uint32_t *>(pixel_pointer_)[1] = mode1_output_[ram_[address+1]];
-							pixel_pointer_ += 8;
+							pixel_pointer_ += 2 * sizeof(uint32_t);
 						break;
 
 						case 2:
 							reinterpret_cast<uint64_t *>(pixel_pointer_)[0] = mode2_output_[ram_[address]];
 							reinterpret_cast<uint64_t *>(pixel_pointer_)[1] = mode2_output_[ram_[address+1]];
-							pixel_pointer_ += 16;
+							pixel_pointer_ += 2 * sizeof(uint64_t);
 						break;
 
 						case 3:
 							reinterpret_cast<uint16_t *>(pixel_pointer_)[0] = mode3_output_[ram_[address]];
 							reinterpret_cast<uint16_t *>(pixel_pointer_)[1] = mode3_output_[ram_[address+1]];
-							pixel_pointer_ += 4;
+							pixel_pointer_ += 2 * sizeof(uint16_t);
 						break;
 
 					}
 
-					// flush the current buffer pixel if full; the CRTC allows many different display
+					// Flush the current buffer pixel if full; the CRTC allows many different display
 					// widths so it's not necessarily possible to predict the correct number in advance
-					// and using the upper bound could lead to inefficient behaviour
+					// and using the upper bound could lead to inefficient behaviour.
 					if(pixel_pointer_ == pixel_data_ + 320) {
-						crt_->output_data(cycles_ * 16, cycles_ * 16 / pixel_divider_);
+						crt_.output_data(cycles_ * 16, size_t(cycles_ * 16 / pixel_divider_));
 						pixel_pointer_ = pixel_data_ = nullptr;
 						cycles_ = 0;
 					}
@@ -323,27 +330,14 @@ class CRTCBusHandler {
 			was_hsync_ = state.hsync;
 		}
 
-		/// Constructs an appropriate CRT for video output.
-		void setup_output(float aspect_ratio) {
-			crt_.reset(new Outputs::CRT::CRT(1024, 16, Outputs::CRT::DisplayType::PAL50, 1));
-			crt_->set_rgb_sampling_function(
-				"vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)"
-				"{"
-					"uint sample = texture(texID, coordinate).r;"
-					"return vec3(float((sample >> 4) & 3u), float((sample >> 2) & 3u), float(sample & 3u)) / 2.0;"
-				"}");
-			crt_->set_visible_area(Outputs::CRT::Rect(0.1072f, 0.1f, 0.842105263157895f, 0.842105263157895f));
-			crt_->set_video_signal(Outputs::CRT::VideoSignal::RGB);
+		/// Sets the destination for output.
+		void set_scan_target(Outputs::Display::ScanTarget *scan_target) {
+			crt_.set_scan_target(scan_target);
 		}
 
-		/// Destructs the CRT.
-		void close_output() {
-			crt_.reset();
-		}
-
-		/// @returns the CRT.
-		Outputs::CRT::CRT *get_crt() {
-			return crt_.get();
+		/// Sets the type of display.
+		void set_display_type(Outputs::Display::DisplayType display_type) {
+			crt_.set_display_type(display_type);
 		}
 
 		/*!
@@ -376,10 +370,18 @@ class CRTCBusHandler {
 		}
 
 	private:
-		void output_border(unsigned int length) {
-			uint8_t *colour_pointer = static_cast<uint8_t *>(crt_->allocate_write_area(1));
-			if(colour_pointer) *colour_pointer = border_;
-			crt_->output_level(length * 16);
+		void output_border(int length) {
+			assert(length >= 0);
+
+			// A black border can be output via crt_.output_blank for a minor performance
+			// win; otherwise paint whatever the border colour really is.
+			if(border_) {
+				uint8_t *const colour_pointer = static_cast<uint8_t *>(crt_.begin_data(1));
+				if(colour_pointer) *colour_pointer = border_;
+				crt_.output_level(length * 16);
+			} else {
+				crt_.output_blank(length * 16);
+			}
 		}
 
 #define Mode0Colour0(c) ((c & 0x80) >> 7) | ((c & 0x20) >> 3) | ((c & 0x08) >> 2) | ((c & 0x02) << 2)
@@ -395,16 +397,16 @@ class CRTCBusHandler {
 
 		void establish_palette_hits() {
 			for(int c = 0; c < 256; c++) {
-				mode0_palette_hits_[Mode0Colour0(c)].push_back(static_cast<uint8_t>(c));
-				mode0_palette_hits_[Mode0Colour1(c)].push_back(static_cast<uint8_t>(c));
+				mode0_palette_hits_[Mode0Colour0(c)].push_back(uint8_t(c));
+				mode0_palette_hits_[Mode0Colour1(c)].push_back(uint8_t(c));
 
-				mode1_palette_hits_[Mode1Colour0(c)].push_back(static_cast<uint8_t>(c));
-				mode1_palette_hits_[Mode1Colour1(c)].push_back(static_cast<uint8_t>(c));
-				mode1_palette_hits_[Mode1Colour2(c)].push_back(static_cast<uint8_t>(c));
-				mode1_palette_hits_[Mode1Colour3(c)].push_back(static_cast<uint8_t>(c));
+				mode1_palette_hits_[Mode1Colour0(c)].push_back(uint8_t(c));
+				mode1_palette_hits_[Mode1Colour1(c)].push_back(uint8_t(c));
+				mode1_palette_hits_[Mode1Colour2(c)].push_back(uint8_t(c));
+				mode1_palette_hits_[Mode1Colour3(c)].push_back(uint8_t(c));
 
-				mode3_palette_hits_[Mode3Colour0(c)].push_back(static_cast<uint8_t>(c));
-				mode3_palette_hits_[Mode3Colour1(c)].push_back(static_cast<uint8_t>(c));
+				mode3_palette_hits_[Mode3Colour0(c)].push_back(uint8_t(c));
+				mode3_palette_hits_[Mode3Colour1(c)].push_back(uint8_t(c));
 			}
 		}
 
@@ -414,7 +416,7 @@ class CRTCBusHandler {
 					// Mode 0: abcdefgh -> [gcea] [hdfb]
 					for(int c = 0; c < 256; c++) {
 						// prepare mode 0
-						uint8_t *mode0_pixels = reinterpret_cast<uint8_t *>(&mode0_output_[c]);
+						uint8_t *const mode0_pixels = reinterpret_cast<uint8_t *>(&mode0_output_[c]);
 						mode0_pixels[0] = palette_[Mode0Colour0(c)];
 						mode0_pixels[1] = palette_[Mode0Colour1(c)];
 					}
@@ -423,7 +425,7 @@ class CRTCBusHandler {
 				case 1:
 					for(int c = 0; c < 256; c++) {
 						// prepare mode 1
-						uint8_t *mode1_pixels = reinterpret_cast<uint8_t *>(&mode1_output_[c]);
+						uint8_t *const mode1_pixels = reinterpret_cast<uint8_t *>(&mode1_output_[c]);
 						mode1_pixels[0] = palette_[Mode1Colour0(c)];
 						mode1_pixels[1] = palette_[Mode1Colour1(c)];
 						mode1_pixels[2] = palette_[Mode1Colour2(c)];
@@ -434,7 +436,7 @@ class CRTCBusHandler {
 				case 2:
 					for(int c = 0; c < 256; c++) {
 						// prepare mode 2
-						uint8_t *mode2_pixels = reinterpret_cast<uint8_t *>(&mode2_output_[c]);
+						uint8_t *const mode2_pixels = reinterpret_cast<uint8_t *>(&mode2_output_[c]);
 						mode2_pixels[0] = palette_[((c & 0x80) >> 7)];
 						mode2_pixels[1] = palette_[((c & 0x40) >> 6)];
 						mode2_pixels[2] = palette_[((c & 0x20) >> 5)];
@@ -449,7 +451,7 @@ class CRTCBusHandler {
 				case 3:
 					for(int c = 0; c < 256; c++) {
 						// prepare mode 3
-						uint8_t *mode3_pixels = reinterpret_cast<uint8_t *>(&mode3_output_[c]);
+						uint8_t *const mode3_pixels = reinterpret_cast<uint8_t *>(&mode3_output_[c]);
 						mode3_pixels[0] = palette_[Mode3Colour0(c)];
 						mode3_pixels[1] = palette_[Mode3Colour1(c)];
 					}
@@ -461,7 +463,7 @@ class CRTCBusHandler {
 			switch(mode_) {
 				case 0: {
 					for(uint8_t c : mode0_palette_hits_[pen]) {
-						uint8_t *mode0_pixels = reinterpret_cast<uint8_t *>(&mode0_output_[c]);
+						uint8_t *const mode0_pixels = reinterpret_cast<uint8_t *>(&mode0_output_[c]);
 						mode0_pixels[0] = palette_[Mode0Colour0(c)];
 						mode0_pixels[1] = palette_[Mode0Colour1(c)];
 					}
@@ -469,7 +471,7 @@ class CRTCBusHandler {
 				case 1:
 					if(pen > 3) return;
 					for(uint8_t c : mode1_palette_hits_[pen]) {
-						uint8_t *mode1_pixels = reinterpret_cast<uint8_t *>(&mode1_output_[c]);
+						uint8_t *const mode1_pixels = reinterpret_cast<uint8_t *>(&mode1_output_[c]);
 						mode1_pixels[0] = palette_[Mode1Colour0(c)];
 						mode1_pixels[1] = palette_[Mode1Colour1(c)];
 						mode1_pixels[2] = palette_[Mode1Colour2(c)];
@@ -486,7 +488,7 @@ class CRTCBusHandler {
 					if(pen > 3) return;
 					// Same argument applies here as to case 1, as the unused bits aren't masked out.
 					for(uint8_t c : mode3_palette_hits_[pen]) {
-						uint8_t *mode3_pixels = reinterpret_cast<uint8_t *>(&mode3_output_[c]);
+						uint8_t *const mode3_pixels = reinterpret_cast<uint8_t *>(&mode3_output_[c]);
 						mode3_pixels[0] = palette_[Mode3Colour0(c)];
 						mode3_pixels[1] = palette_[Mode3Colour1(c)];
 					}
@@ -507,7 +509,7 @@ class CRTCBusHandler {
 
 		uint8_t mapped_palette_value(uint8_t colour) {
 #define COL(r, g, b) (r << 4) | (g << 2) | b
-			static const uint8_t mapping[32] = {
+			constexpr uint8_t mapping[32] = {
 				COL(1, 1, 1),	COL(1, 1, 1),	COL(0, 2, 1),	COL(2, 2, 1),
 				COL(0, 0, 1),	COL(2, 0, 1),	COL(0, 1, 1),	COL(2, 1, 1),
 				COL(2, 0, 1),	COL(2, 2, 1),	COL(2, 2, 0),	COL(2, 2, 2),
@@ -528,19 +530,19 @@ class CRTCBusHandler {
 			Border,
 			Pixels
 		} previous_output_mode_ = OutputMode::Sync;
-		unsigned int cycles_ = 0;
+		int cycles_ = 0;
 
 		bool was_hsync_ = false, was_vsync_ = false;
 		int cycles_into_hsync_ = 0;
 
-		std::unique_ptr<Outputs::CRT::CRT> crt_;
+		Outputs::CRT::CRT crt_;
 		uint8_t *pixel_data_ = nullptr, *pixel_pointer_ = nullptr;
 
-		uint8_t *ram_ = nullptr;
+		const uint8_t *const ram_ = nullptr;
 
 		int next_mode_ = 2, mode_ = 2;
 
-		unsigned int pixel_divider_ = 1;
+		int pixel_divider_ = 1;
 		uint16_t mode0_output_[256];
 		uint32_t mode1_output_[256];
 		uint64_t mode2_output_[256];
@@ -572,7 +574,7 @@ class KeyboardState: public GI::AY38910::PortHandler {
 			Sets the row currently being reported to the AY.
 		*/
 		void set_row(int row) {
-			row_ = static_cast<size_t>(row);
+			row_ = size_t(row);
 		}
 
 		/*!
@@ -591,7 +593,7 @@ class KeyboardState: public GI::AY38910::PortHandler {
 		*/
 		void set_is_pressed(bool is_pressed, int line, int key) {
 			int mask = 1 << key;
-			assert(static_cast<size_t>(line) < sizeof(rows_));
+			assert(size_t(line) < sizeof(rows_));
 			if(is_pressed) rows_[line] &= ~mask; else rows_[line] |= mask;
 		}
 
@@ -602,7 +604,7 @@ class KeyboardState: public GI::AY38910::PortHandler {
 			memset(rows_, 0xff, sizeof(rows_));
 		}
 
-		std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() {
+		const std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() {
 			return joysticks_;
 		}
 
@@ -757,7 +759,7 @@ class i8255PortHandler : public Intel::i8255::PortHandler {
 template <bool has_fdc> class ConcreteMachine:
 	public CRTMachine::Machine,
 	public MediaTarget::Machine,
-	public KeyboardMachine::Machine,
+	public KeyboardMachine::MappedMachine,
 	public Utility::TypeRecipient,
 	public CPU::Z80::BusHandler,
 	public ClockingHint::Observer,
@@ -789,33 +791,43 @@ template <bool has_fdc> class ConcreteMachine:
 			ay_.ay().set_port_handler(&key_state_);
 
 			// construct the list of necessary ROMs
-			std::vector<std::string> required_roms = {"amsdos.rom"};
+			const std::string machine_name = "AmstradCPC";
+			std::vector<ROMMachine::ROM> required_roms = {
+				ROMMachine::ROM(machine_name, "the Amstrad Disk Operating System", "amsdos.rom", 16*1024, 0x1fe22ecd)
+			};
 			std::string model_number;
+			uint32_t crcs[2];
 			switch(target.model) {
 				default:
 					model_number = "6128";
 					has_128k_ = true;
+					crcs[0] = 0x0219bb74;
+					crcs[1] = 0xca6af63d;
 				break;
 				case Analyser::Static::AmstradCPC::Target::Model::CPC464:
 					model_number = "464";
 					has_128k_ = false;
+					crcs[0] = 0x815752df;
+					crcs[1] = 0x7d9a3bac;
 				break;
 				case Analyser::Static::AmstradCPC::Target::Model::CPC664:
 					model_number = "664";
 					has_128k_ = false;
+					crcs[0] = 0x3f5a6dc4;
+					crcs[1] = 0x32fee492;
 				break;
 			}
-			required_roms.push_back("os" + model_number + ".rom");
-			required_roms.push_back("basic" + model_number + ".rom");
+			required_roms.emplace_back(machine_name, "the CPC " + model_number + " firmware", "os" + model_number + ".rom", 16*1024, crcs[0]);
+			required_roms.emplace_back(machine_name, "the CPC " + model_number + " BASIC ROM", "basic" + model_number + ".rom", 16*1024, crcs[1]);
 
 			// fetch and verify the ROMs
-			const auto roms = rom_fetcher("AmstradCPC", required_roms);
+			const auto roms = rom_fetcher(required_roms);
 
 			for(std::size_t index = 0; index < roms.size(); ++index) {
 				auto &data = roms[index];
 				if(!data) throw ROMMachine::Error::MissingROMs;
-				roms_[static_cast<int>(index)] = std::move(*data);
-				roms_[static_cast<int>(index)].resize(16384);
+				roms_[int(index)] = std::move(*data);
+				roms_[int(index)].resize(16384);
 			}
 
 			// Establish default memory map
@@ -860,13 +872,15 @@ template <bool has_fdc> class ConcreteMachine:
 
 			// TODO (in the player, not here): adapt it to accept an input clock rate and
 			// run_for as HalfCycles
-			if(!tape_player_is_sleeping_) tape_player_.run_for(cycle.length.as_int());
+			if(!tape_player_is_sleeping_) tape_player_.run_for(cycle.length.as_integral());
 
 			// Pump the AY
 			ay_.run_for(cycle.length);
 
-			// Clock the FDC, if connected, using a lazy scale by two
-			time_since_fdc_update_ += cycle.length;
+			if constexpr (has_fdc) {
+				// Clock the FDC, if connected, using a lazy scale by two
+				time_since_fdc_update_ += cycle.length;
+			}
 
 			// Update typing activity
 			if(typer_) typer_->run_for(cycle.length);
@@ -892,9 +906,11 @@ template <bool has_fdc> class ConcreteMachine:
 					}
 
 					// Check for an upper ROM selection
-					if(has_fdc && !(address&0x2000)) {
-						upper_rom_ = (*cycle.value == 7) ? ROMType::AMSDOS : ROMType::BASIC;
-						if(upper_rom_is_paged_) read_pointers_[3] = roms_[upper_rom_].data();
+					if constexpr (has_fdc) {
+						if(!(address&0x2000)) {
+							upper_rom_ = (*cycle.value == 7) ? ROMType::AMSDOS : ROMType::BASIC;
+							if(upper_rom_is_paged_) read_pointers_[3] = roms_[upper_rom_].data();
+						}
 					}
 
 					// Check for a CRTC access
@@ -908,19 +924,21 @@ template <bool has_fdc> class ConcreteMachine:
 
 					// Check for an 8255 PIO access
 					if(!(address & 0x800)) {
-						i8255_.set_register((address >> 8) & 3, *cycle.value);
+						i8255_.write((address >> 8) & 3, *cycle.value);
 					}
 
-					// Check for an FDC access
-					if(has_fdc && (address & 0x580) == 0x100) {
-						flush_fdc();
-						fdc_.set_register(address & 1, *cycle.value);
-					}
+					if constexpr (has_fdc) {
+						// Check for an FDC access
+						if((address & 0x580) == 0x100) {
+							flush_fdc();
+							fdc_.write(address & 1, *cycle.value);
+						}
 
-					// Check for a disk motor access
-					if(has_fdc && !(address & 0x580)) {
-						flush_fdc();
-						fdc_.set_motor_on(!!(*cycle.value));
+						// Check for a disk motor access
+						if(!(address & 0x580)) {
+							flush_fdc();
+							fdc_.set_motor_on(!!(*cycle.value));
+						}
 					}
 				break;
 				case CPU::Z80::PartialMachineCycle::Input:
@@ -929,13 +947,15 @@ template <bool has_fdc> class ConcreteMachine:
 
 					// Check for a PIO access
 					if(!(address & 0x800)) {
-						*cycle.value &= i8255_.get_register((address >> 8) & 3);
+						*cycle.value &= i8255_.read((address >> 8) & 3);
 					}
 
 					// Check for an FDC access
-					if(has_fdc && (address & 0x580) == 0x100) {
-						flush_fdc();
-						*cycle.value &= fdc_.get_register(address & 1);
+					if constexpr (has_fdc) {
+						if((address & 0x580) == 0x100) {
+							flush_fdc();
+							*cycle.value &= fdc_.read(address & 1);
+						}
 					}
 
 					// Check for a CRTC access; the below is not a typo, the CRTC can be selected
@@ -981,19 +1001,14 @@ template <bool has_fdc> class ConcreteMachine:
 			flush_fdc();
 		}
 
-		/// A CRTMachine function; indicates that outputs should be created now.
-		void setup_output(float aspect_ratio) override final {
-			crtc_bus_handler_.setup_output(aspect_ratio);
+		/// A CRTMachine function; sets the destination for video.
+		void set_scan_target(Outputs::Display::ScanTarget *scan_target) override final {
+			crtc_bus_handler_.set_scan_target(scan_target);
 		}
 
-		/// A CRTMachine function; indicates that outputs should be destroyed now.
-		void close_output() override final {
-			crtc_bus_handler_.close_output();
-		}
-
-		/// @returns the CRT in use.
-		Outputs::CRT::CRT *get_crt() override final {
-			return crtc_bus_handler_.get_crt();
+		/// A CRTMachine function; sets the output display type.
+		void set_display_type(Outputs::Display::DisplayType display_type) override final {
+			crtc_bus_handler_.set_display_type(display_type);
 		}
 
 		/// @returns the speaker in use.
@@ -1058,7 +1073,7 @@ template <bool has_fdc> class ConcreteMachine:
 
 		// MARK: - Activity Source
 		void set_activity_observer(Activity::Observer *observer) override {
-			if(has_fdc) fdc_.set_activity_observer(observer);
+			if constexpr (has_fdc) fdc_.set_activity_observer(observer);
 		}
 
 		// MARK: - Configuration options.
@@ -1086,7 +1101,7 @@ template <bool has_fdc> class ConcreteMachine:
 		}
 
 		// MARK: - Joysticks
-		std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() override {
+		const std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() override {
 			return key_state_.get_joysticks();
 		}
 
@@ -1148,11 +1163,13 @@ template <bool has_fdc> class ConcreteMachine:
 		FDC fdc_;
 		HalfCycles time_since_fdc_update_;
 		void flush_fdc() {
-			// Clock the FDC, if connected, using a lazy scale by two
-			if(has_fdc && !fdc_is_sleeping_) {
-				fdc_.run_for(Cycles(time_since_fdc_update_.as_int()));
+			if constexpr (has_fdc) {
+				// Clock the FDC, if connected, using a lazy scale by two
+				if(!fdc_is_sleeping_) {
+					fdc_.run_for(Cycles(time_since_fdc_update_.as_integral()));
+				}
+				time_since_fdc_update_ = HalfCycles(0);
 			}
-			time_since_fdc_update_ = HalfCycles(0);
 		}
 
 		InterruptTimer interrupt_timer_;
@@ -1192,7 +1209,7 @@ Machine *Machine::AmstradCPC(const Analyser::Static::Target *target, const ROMMa
 	using Target = Analyser::Static::AmstradCPC::Target;
 	const Target *const cpc_target = dynamic_cast<const Target *>(target);
 	switch(cpc_target->model) {
-		default: 					return new AmstradCPC::ConcreteMachine<true>(*cpc_target, rom_fetcher);
+		default:					return new AmstradCPC::ConcreteMachine<true>(*cpc_target, rom_fetcher);
 		case Target::Model::CPC464:	return new AmstradCPC::ConcreteMachine<false>(*cpc_target, rom_fetcher);
 	}
 }

Machines/AmstradCPC/Keyboard.cpp

@@ -31,12 +31,12 @@ uint16_t KeyboardMapper::mapped_key_for_key(Inputs::Keyboard::Key key) {
 		BIND(F11, KeyRightSquareBracket);
 		BIND(F12, KeyClear);
 
-		BIND(Hyphen, KeyMinus);		BIND(Equals, KeyCaret);		BIND(BackSpace, KeyDelete);
+		BIND(Hyphen, KeyMinus);		BIND(Equals, KeyCaret);		BIND(Backspace, KeyDelete);
 		BIND(Tab, KeyTab);
 
 		BIND(OpenSquareBracket, KeyAt);
 		BIND(CloseSquareBracket, KeyLeftSquareBracket);
-		BIND(BackSlash, KeyBackSlash);
+		BIND(Backslash, KeyBackSlash);
 
 		BIND(CapsLock, KeyCapsLock);
 		BIND(Semicolon, KeyColon);
@@ -57,27 +57,27 @@ uint16_t KeyboardMapper::mapped_key_for_key(Inputs::Keyboard::Key key) {
 		BIND(Left, KeyLeft);	BIND(Right, KeyRight);
 		BIND(Up, KeyUp);		BIND(Down, KeyDown);
 
-		BIND(KeyPad0, KeyF0);
-		BIND(KeyPad1, KeyF1);		BIND(KeyPad2, KeyF2);		BIND(KeyPad3, KeyF3);
-		BIND(KeyPad4, KeyF4);		BIND(KeyPad5, KeyF5);		BIND(KeyPad6, KeyF6);
-		BIND(KeyPad7, KeyF7);		BIND(KeyPad8, KeyF8);		BIND(KeyPad9, KeyF9);
-		BIND(KeyPadPlus, KeySemicolon);
-		BIND(KeyPadMinus, KeyMinus);
+		BIND(Keypad0, KeyF0);
+		BIND(Keypad1, KeyF1);		BIND(Keypad2, KeyF2);		BIND(Keypad3, KeyF3);
+		BIND(Keypad4, KeyF4);		BIND(Keypad5, KeyF5);		BIND(Keypad6, KeyF6);
+		BIND(Keypad7, KeyF7);		BIND(Keypad8, KeyF8);		BIND(Keypad9, KeyF9);
+		BIND(KeypadPlus, KeySemicolon);
+		BIND(KeypadMinus, KeyMinus);
 
-		BIND(KeyPadEnter, KeyEnter);
-		BIND(KeyPadDecimalPoint, KeyFullStop);
-		BIND(KeyPadEquals, KeyMinus);
-		BIND(KeyPadSlash, KeyForwardSlash);
-		BIND(KeyPadAsterisk, KeyColon);
-		BIND(KeyPadDelete, KeyDelete);
+		BIND(KeypadEnter, KeyEnter);
+		BIND(KeypadDecimalPoint, KeyFullStop);
+		BIND(KeypadEquals, KeyMinus);
+		BIND(KeypadSlash, KeyForwardSlash);
+		BIND(KeypadAsterisk, KeyColon);
+		BIND(KeypadDelete, KeyDelete);
 	}
 #undef BIND
 }
 
 uint16_t *CharacterMapper::sequence_for_character(char character) {
-#define KEYS(...)	{__VA_ARGS__, KeyboardMachine::Machine::KeyEndSequence}
-#define SHIFT(...)	{KeyShift, __VA_ARGS__, KeyboardMachine::Machine::KeyEndSequence}
-#define X			{KeyboardMachine::Machine::KeyNotMapped}
+#define KEYS(...)	{__VA_ARGS__, KeyboardMachine::MappedMachine::KeyEndSequence}
+#define SHIFT(...)	{KeyShift, __VA_ARGS__, KeyboardMachine::MappedMachine::KeyEndSequence}
+#define X			{KeyboardMachine::MappedMachine::KeyNotMapped}
 	static KeySequence key_sequences[] = {
 		/* NUL */	X,							/* SOH */	X,
 		/* STX */	X,							/* ETX */	X,

Machines/AmstradCPC/Keyboard.hpp

@@ -33,7 +33,7 @@ enum Key: uint16_t {
 #undef Line
 };
 
-struct KeyboardMapper: public KeyboardMachine::Machine::KeyboardMapper {
+struct KeyboardMapper: public KeyboardMachine::MappedMachine::KeyboardMapper {
 	uint16_t mapped_key_for_key(Inputs::Keyboard::Key key);
 };
 

Machines/Apple/AppleII/AppleII.cpp

@@ -8,74 +8,86 @@
 
 #include "AppleII.hpp"
 
-#include "../../Activity/Source.hpp"
-#include "../MediaTarget.hpp"
-#include "../CRTMachine.hpp"
-#include "../JoystickMachine.hpp"
-#include "../KeyboardMachine.hpp"
-#include "../Utility/MemoryFuzzer.hpp"
-#include "../Utility/StringSerialiser.hpp"
+#include "../../../Activity/Source.hpp"
+#include "../../MediaTarget.hpp"
+#include "../../CRTMachine.hpp"
+#include "../../JoystickMachine.hpp"
+#include "../../KeyboardMachine.hpp"
+#include "../../Utility/MemoryFuzzer.hpp"
+#include "../../Utility/StringSerialiser.hpp"
 
-#include "../../Processors/6502/6502.hpp"
-#include "../../Components/AudioToggle/AudioToggle.hpp"
+#include "../../../Processors/6502/6502.hpp"
+#include "../../../Components/AudioToggle/AudioToggle.hpp"
 
-#include "../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
+#include "../../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
+#include "../../../Outputs/Log.hpp"
 
 #include "Card.hpp"
 #include "DiskIICard.hpp"
 #include "Video.hpp"
 
-#include "../../Analyser/Static/AppleII/Target.hpp"
-#include "../../ClockReceiver/ForceInline.hpp"
+#include "../../../Analyser/Static/AppleII/Target.hpp"
+#include "../../../ClockReceiver/ForceInline.hpp"
+#include "../../../Configurable/StandardOptions.hpp"
 
 #include <algorithm>
 #include <array>
 #include <memory>
 
-namespace {
+namespace Apple {
+namespace II {
 
-template <bool is_iie> class ConcreteMachine:
+std::vector<std::unique_ptr<Configurable::Option>> get_options() {
+	return Configurable::standard_options(
+		static_cast<Configurable::StandardOptions>(Configurable::DisplayCompositeMonochrome | Configurable::DisplayCompositeColour)
+	);
+}
+
+#define is_iie() ((model == Analyser::Static::AppleII::Target::Model::IIe) || (model == Analyser::Static::AppleII::Target::Model::EnhancedIIe))
+
+template <Analyser::Static::AppleII::Target::Model model> class ConcreteMachine:
 	public CRTMachine::Machine,
 	public MediaTarget::Machine,
-	public KeyboardMachine::Machine,
+	public KeyboardMachine::MappedMachine,
 	public CPU::MOS6502::BusHandler,
 	public Inputs::Keyboard,
-	public AppleII::Machine,
+	public Configurable::Device,
+	public Apple::II::Machine,
 	public Activity::Source,
 	public JoystickMachine::Machine,
-	public AppleII::Card::Delegate {
+	public Apple::II::Card::Delegate {
 	private:
-		struct VideoBusHandler : public AppleII::Video::BusHandler {
+		struct VideoBusHandler : public Apple::II::Video::BusHandler {
 			public:
 				VideoBusHandler(uint8_t *ram, uint8_t *aux_ram) : ram_(ram), aux_ram_(aux_ram) {}
 
-				uint8_t perform_read(uint16_t address) {
-					return ram_[address];
-				}
-				uint16_t perform_aux_read(uint16_t address) {
-					return static_cast<uint16_t>(ram_[address] | (aux_ram_[address] << 8));
+				void perform_read(uint16_t address, size_t count, uint8_t *base_target, uint8_t *auxiliary_target) {
+					memcpy(base_target, &ram_[address], count);
+					memcpy(auxiliary_target, &aux_ram_[address], count);
 				}
 
 			private:
 				uint8_t *ram_, *aux_ram_;
 		};
 
-		CPU::MOS6502::Processor<ConcreteMachine, false> m6502_;
+		CPU::MOS6502::Processor<(model == Analyser::Static::AppleII::Target::Model::EnhancedIIe) ? CPU::MOS6502::Personality::PSynertek65C02 : CPU::MOS6502::Personality::P6502, ConcreteMachine, false> m6502_;
 		VideoBusHandler video_bus_handler_;
-		std::unique_ptr<AppleII::Video::Video<VideoBusHandler, is_iie>> video_;
+		Apple::II::Video::Video<VideoBusHandler, is_iie()> video_;
 		int cycles_into_current_line_ = 0;
 		Cycles cycles_since_video_update_;
 
 		void update_video() {
-			video_->run_for(cycles_since_video_update_.flush());
+			video_.run_for(cycles_since_video_update_.flush<Cycles>());
 		}
-		static const int audio_divider = 8;
+		static constexpr int audio_divider = 8;
 		void update_audio() {
 			speaker_.run_for(audio_queue_, cycles_since_audio_update_.divide(Cycles(audio_divider)));
 		}
 		void update_just_in_time_cards() {
-			for(const auto &card : just_in_time_cards_) {
-				card->run_for(cycles_since_card_update_, stretched_cycles_since_card_update_);
+			if(cycles_since_card_update_ > Cycles(0)) {
+				for(const auto &card : just_in_time_cards_) {
+					card->run_for(cycles_since_card_update_, stretched_cycles_since_card_update_);
+				}
 			}
 			cycles_since_card_update_ = 0;
 			stretched_cycles_since_card_update_ = 0;
@@ -83,51 +95,64 @@ template <bool is_iie> class ConcreteMachine:
 
 		uint8_t ram_[65536], aux_ram_[65536];
 		std::vector<uint8_t> rom_;
-		std::vector<uint8_t> character_rom_;
 		uint8_t keyboard_input_ = 0x00;
 		bool key_is_down_ = false;
 
+		uint8_t get_keyboard_input() {
+			if(string_serialiser_) {
+				return string_serialiser_->head() | 0x80;
+			} else {
+				return keyboard_input_;
+			}
+		}
+
 		Concurrency::DeferringAsyncTaskQueue audio_queue_;
 		Audio::Toggle audio_toggle_;
 		Outputs::Speaker::LowpassSpeaker<Audio::Toggle> speaker_;
 		Cycles cycles_since_audio_update_;
 
 		// MARK: - Cards
-		std::array<std::unique_ptr<AppleII::Card>, 7> cards_;
+		std::array<std::unique_ptr<Apple::II::Card>, 7> cards_;
 		Cycles cycles_since_card_update_;
-		std::vector<AppleII::Card *> every_cycle_cards_;
-		std::vector<AppleII::Card *> just_in_time_cards_;
+		std::vector<Apple::II::Card *> every_cycle_cards_;
+		std::vector<Apple::II::Card *> just_in_time_cards_;
 
 		int stretched_cycles_since_card_update_ = 0;
 
-		void install_card(std::size_t slot, AppleII::Card *card) {
+		void install_card(std::size_t slot, Apple::II::Card *card) {
 			assert(slot >= 1 && slot < 8);
 			cards_[slot - 1].reset(card);
 			card->set_delegate(this);
 			pick_card_messaging_group(card);
 		}
 
-		bool is_every_cycle_card(AppleII::Card *card) {
+		bool is_every_cycle_card(const Apple::II::Card *card) {
 			return !card->get_select_constraints();
 		}
 
-		void pick_card_messaging_group(AppleII::Card *card) {
+		bool card_lists_are_dirty_ = true;
+		bool card_became_just_in_time_ = false;
+		void pick_card_messaging_group(Apple::II::Card *card) {
+			// Simplify to a card being either just-in-time or realtime.
+			// Don't worry about exactly what it's watching,
 			const bool is_every_cycle = is_every_cycle_card(card);
-			std::vector<AppleII::Card *> &intended = is_every_cycle ? every_cycle_cards_ : just_in_time_cards_;
-		 	std::vector<AppleII::Card *> &undesired = is_every_cycle ? just_in_time_cards_ : every_cycle_cards_;
+			std::vector<Apple::II::Card *> &intended = is_every_cycle ? every_cycle_cards_ : just_in_time_cards_;
 
+			// If the card is already in the proper group, stop.
 			if(std::find(intended.begin(), intended.end(), card) != intended.end()) return;
-			auto old_membership = std::find(undesired.begin(), undesired.end(), card);
-			if(old_membership != undesired.end()) undesired.erase(old_membership);
-			intended.push_back(card);
+
+			// Otherwise, mark the sets as dirty. It isn't safe to transition the card here,
+			// as the main loop may be part way through iterating the two lists.
+			card_lists_are_dirty_ = true;
+			card_became_just_in_time_ |= !is_every_cycle;
 		}
 
-		void card_did_change_select_constraints(AppleII::Card *card) override {
+		void card_did_change_select_constraints(Apple::II::Card *card) override {
 			pick_card_messaging_group(card);
 		}
 
-		AppleII::DiskIICard *diskii_card() {
-			return dynamic_cast<AppleII::DiskIICard *>(cards_[5].get());
+		Apple::II::DiskIICard *diskii_card() {
+			return dynamic_cast<Apple::II::DiskIICard *>(cards_[5].get());
 		}
 
 		// MARK: - Memory Map.
@@ -145,7 +170,7 @@ template <bool is_iie> class ConcreteMachine:
 
 			On a IIe with auxiliary memory the following orthogonal changes also need to be factored in:
 
-			0000 to 0200 	:	can be paged independently of the rest of RAM, other than part of the language card area which pages with it
+			0000 to 0200	:	can be paged independently of the rest of RAM, other than part of the language card area which pages with it
 			0400 to 0800	:	the text screen, can be configured to write to auxiliary RAM
 			2000 to 4000	:	the graphics screen, which can be configured to write to auxiliary RAM
 			c100 to d000	:	can be used to page an additional 3.75kb of ROM, replacing the IO area
@@ -179,7 +204,7 @@ template <bool is_iie> class ConcreteMachine:
 		bool has_language_card_ = true;
 		void set_language_card_paging() {
 			uint8_t *const ram = alternative_zero_page_ ? aux_ram_ : ram_;
-			uint8_t *const rom = is_iie ? &rom_[3840] : rom_.data();
+			uint8_t *const rom = is_iie() ? &rom_[3840] : rom_.data();
 
 			page(0xd0, 0xe0,
 				language_card_.read ? &ram[language_card_.bank1 ? 0xd000 : 0xc000] : rom,
@@ -225,13 +250,13 @@ template <bool is_iie> class ConcreteMachine:
 				read_auxiliary_memory_ ? &aux_ram_[0x0200] : &ram_[0x0200],
 				write_auxiliary_memory_ ? &aux_ram_[0x0200] : &ram_[0x0200]);
 
-			if(video_ && video_->get_80_store()) {
-				bool use_aux_ram = video_->get_page2();
+			if(video_.get_80_store()) {
+				bool use_aux_ram = video_.get_page2();
 				page(0x04, 0x08,
 					use_aux_ram ? &aux_ram_[0x0400] : &ram_[0x0400],
 					use_aux_ram ? &aux_ram_[0x0400] : &ram_[0x0400]);
 
-				if(video_->get_high_resolution()) {
+				if(video_.get_high_resolution()) {
 					page(0x20, 0x40,
 						use_aux_ram ? &aux_ram_[0x2000] : &ram_[0x2000],
 						use_aux_ram ? &aux_ram_[0x2000] : &ram_[0x2000]);
@@ -298,16 +323,17 @@ template <bool is_iie> class ConcreteMachine:
 
 	public:
 		ConcreteMachine(const Analyser::Static::AppleII::Target &target, const ROMMachine::ROMFetcher &rom_fetcher):
-		 	m6502_(*this),
-		 	video_bus_handler_(ram_, aux_ram_),
-		 	audio_toggle_(audio_queue_),
-		 	speaker_(audio_toggle_) {
-		 	// The system's master clock rate.
-		 	const float master_clock = 14318180.0;
+			m6502_(*this),
+			video_bus_handler_(ram_, aux_ram_),
+			video_(video_bus_handler_),
+			audio_toggle_(audio_queue_),
+			speaker_(audio_toggle_) {
+			// The system's master clock rate.
+			constexpr float master_clock = 14318180.0;
 
-		 	// This is where things get slightly convoluted: establish the machine as having a clock rate
-		 	// equal to the number of cycles of work the 6502 will actually achieve. Which is less than
-		 	// the master clock rate divided by 14 because every 65th cycle is extended by one seventh.
+			// This is where things get slightly convoluted: establish the machine as having a clock rate
+			// equal to the number of cycles of work the 6502 will actually achieve. Which is less than
+			// the master clock rate divided by 14 because every 65th cycle is extended by one seventh.
 			set_clock_rate((master_clock / 14.0) * 65.0 / (65.0 + 1.0 / 7.0));
 
 			// The speaker, however, should think it is clocked at half the master clock, per a general
@@ -324,30 +350,44 @@ template <bool is_iie> class ConcreteMachine:
 			Memory::Fuzz(aux_ram_, sizeof(aux_ram_));
 
 			// Add a couple of joysticks.
-		 	joysticks_.emplace_back(new Joystick);
-		 	joysticks_.emplace_back(new Joystick);
+			joysticks_.emplace_back(new Joystick);
+			joysticks_.emplace_back(new Joystick);
 
 			// Pick the required ROMs.
 			using Target = Analyser::Static::AppleII::Target;
-			std::vector<std::string> rom_names;
+			const std::string machine_name = "AppleII";
+			std::vector<ROMMachine::ROM> rom_descriptions;
 			size_t rom_size = 12*1024;
 			switch(target.model) {
 				default:
-					rom_names.push_back("apple2-character.rom");
-					rom_names.push_back("apple2o.rom");
+					rom_descriptions.emplace_back(machine_name, "the basic Apple II character ROM", "apple2-character.rom", 2*1024, 0x64f415c6);
+					rom_descriptions.emplace_back(machine_name, "the original Apple II ROM", "apple2o.rom", 12*1024, 0xba210588);
 				break;
 				case Target::Model::IIplus:
-					rom_names.push_back("apple2-character.rom");
-					rom_names.push_back("apple2.rom");
+					rom_descriptions.emplace_back(machine_name, "the basic Apple II character ROM", "apple2-character.rom", 2*1024, 0x64f415c6);
+					rom_descriptions.emplace_back(machine_name, "the Apple II+ ROM", "apple2.rom", 12*1024, 0xf66f9c26);
 				break;
 				case Target::Model::IIe:
 					rom_size += 3840;
-					rom_names.push_back("apple2eu-character.rom");
-					rom_names.push_back("apple2eu.rom");
+					rom_descriptions.emplace_back(machine_name, "the Apple IIe character ROM", "apple2eu-character.rom", 4*1024, 0x816a86f1);
+					rom_descriptions.emplace_back(machine_name, "the Apple IIe ROM", "apple2eu.rom", 32*1024, 0xe12be18d);
+				break;
+				case Target::Model::EnhancedIIe:
+					rom_size += 3840;
+					rom_descriptions.emplace_back(machine_name, "the Enhanced Apple IIe character ROM", "apple2e-character.rom", 4*1024, 0x2651014d);
+					rom_descriptions.emplace_back(machine_name, "the Enhanced Apple IIe ROM", "apple2e.rom", 32*1024, 0x65989942);
 				break;
 			}
-			const auto roms = rom_fetcher("AppleII", rom_names);
+			const auto roms = rom_fetcher(rom_descriptions);
 
+			// Try to install a Disk II card now, before checking the ROM list,
+			// to make sure that Disk II dependencies have been communicated.
+			if(target.disk_controller != Target::DiskController::None) {
+				// Apple recommended slot 6 for the (first) Disk II.
+				install_card(6, new Apple::II::DiskIICard(rom_fetcher, target.disk_controller == Target::DiskController::SixteenSector));
+			}
+
+			// Now, check and move the ROMs.
 			if(!roms[0] || !roms[1]) {
 				throw ROMMachine::Error::MissingROMs;
 			}
@@ -357,12 +397,7 @@ template <bool is_iie> class ConcreteMachine:
 				rom_.erase(rom_.begin(), rom_.end() - static_cast<off_t>(rom_size));
 			}
 
-			character_rom_ = std::move(*roms[0]);
-
-			if(target.disk_controller != Target::DiskController::None) {
-				// Apple recommended slot 6 for the (first) Disk II.
-				install_card(6, new AppleII::DiskIICard(rom_fetcher, target.disk_controller == Target::DiskController::SixteenSector));
-			}
+			video_.set_character_rom(*roms[0]);
 
 			// Set up the default memory blocks. On a II or II+ these values will never change.
 			// On a IIe they'll be affected by selection of auxiliary RAM.
@@ -382,17 +417,13 @@ template <bool is_iie> class ConcreteMachine:
 			audio_queue_.flush();
 		}
 
-		void setup_output(float aspect_ratio) override {
-			video_.reset(new AppleII::Video::Video<VideoBusHandler, is_iie>(video_bus_handler_));
-			video_->set_character_rom(character_rom_);
+		void set_scan_target(Outputs::Display::ScanTarget *scan_target) override {
+			video_.set_scan_target(scan_target);
 		}
 
-		void close_output() override {
-			video_.reset();
-		}
-
-		Outputs::CRT::CRT *get_crt() override {
-			return video_->get_crt();
+		/// Sets the type of display.
+		void set_display_type(Outputs::Display::DisplayType display_type) override {
+			video_.set_display_type(display_type);
 		}
 
 		Outputs::Speaker::Speaker *get_speaker() override {
@@ -420,9 +451,12 @@ template <bool is_iie> class ConcreteMachine:
 			bool has_updated_cards = false;
 			if(read_pages_[address >> 8]) {
 				if(isReadOperation(operation)) *value = read_pages_[address >> 8][address & 0xff];
-				else if(write_pages_[address >> 8]) write_pages_[address >> 8][address & 0xff] = *value;
+				else {
+					if(address >= 0x200 && address < 0x6000) update_video();
+					if(write_pages_[address >> 8]) write_pages_[address >> 8][address & 0xff] = *value;
+				}
 
-				if(is_iie && address >= 0xc300 && address < 0xd000) {
+				if(is_iie() && address >= 0xc300 && address < 0xd000) {
 					bool internal_c8_rom = internal_c8_rom_;
 					internal_c8_rom |= ((address >> 8) == 0xc3) && !slot_C3_rom_;
 					internal_c8_rom &= (address != 0xcfff);
@@ -446,7 +480,7 @@ template <bool is_iie> class ConcreteMachine:
 				// actor, but this will actually be the result most of the time so it's not
 				// too terrible.
 				if(isReadOperation(operation) && address != 0xc000) {
-					*value = video_->get_last_read_value(cycles_since_video_update_);
+					*value = video_.get_last_read_value(cycles_since_video_update_);
 				}
 
 				switch(address) {
@@ -457,18 +491,18 @@ template <bool is_iie> class ConcreteMachine:
 								default: break;
 
 								case 0xc000:
-									if(string_serialiser_) {
-										*value = string_serialiser_->head() | 0x80;
-									} else {
-										*value = keyboard_input_;
-									}
+									*value = get_keyboard_input();
+								break;
+								case 0xc001: case 0xc002: case 0xc003: case 0xc004: case 0xc005: case 0xc006: case 0xc007:
+								case 0xc008: case 0xc009: case 0xc00a: case 0xc00b: case 0xc00c: case 0xc00d: case 0xc00e: case 0xc00f:
+									*value = (*value & 0x80) | (get_keyboard_input() & 0x7f);
 								break;
 
 								case 0xc061:	// Switch input 0.
 									*value &= 0x7f;
 									if(
 										static_cast<Joystick *>(joysticks_[0].get())->buttons[0] || static_cast<Joystick *>(joysticks_[1].get())->buttons[2] ||
-										(is_iie && open_apple_is_pressed_)
+										(is_iie() && open_apple_is_pressed_)
 									)
 										*value |= 0x80;
 								break;
@@ -476,7 +510,7 @@ template <bool is_iie> class ConcreteMachine:
 									*value &= 0x7f;
 									if(
 										static_cast<Joystick *>(joysticks_[0].get())->buttons[1] || static_cast<Joystick *>(joysticks_[1].get())->buttons[1] ||
-										(is_iie && closed_apple_is_pressed_)
+										(is_iie() && closed_apple_is_pressed_)
 									)
 										*value |= 0x80;
 								break;
@@ -498,33 +532,38 @@ template <bool is_iie> class ConcreteMachine:
 								} break;
 
 								// The IIe-only state reads follow...
-								case 0xc011:	if(is_iie) *value = (*value & 0x7f) | (language_card_.bank1 ? 0x80 : 0x00);											break;
-								case 0xc012:	if(is_iie) *value = (*value & 0x7f) | (language_card_.read ? 0x80 : 0x00);											break;
-								case 0xc013:	if(is_iie) *value = (*value & 0x7f) | (read_auxiliary_memory_ ? 0x80 : 0x00);										break;
-								case 0xc014:	if(is_iie) *value = (*value & 0x7f) | (write_auxiliary_memory_ ? 0x80 : 0x00);										break;
-								case 0xc015:	if(is_iie) *value = (*value & 0x7f) | (internal_CX_rom_ ? 0x80 : 0x00);												break;
-								case 0xc016:	if(is_iie) *value = (*value & 0x7f) | (alternative_zero_page_ ? 0x80 : 0x00);										break;
-								case 0xc017:	if(is_iie) *value = (*value & 0x7f) | (slot_C3_rom_ ? 0x80 : 0x00);													break;
-								case 0xc018:	if(is_iie) *value = (*value & 0x7f) | (video_->get_80_store() ? 0x80 : 0x00);										break;
-								case 0xc019:	if(is_iie) *value = (*value & 0x7f) | (video_->get_is_vertical_blank(cycles_since_video_update_) ? 0x00 : 0x80);	break;
-								case 0xc01a:	if(is_iie) *value = (*value & 0x7f) | (video_->get_text() ? 0x80 : 0x00);											break;
-								case 0xc01b:	if(is_iie) *value = (*value & 0x7f) | (video_->get_mixed() ? 0x80 : 0x00);											break;
-								case 0xc01c:	if(is_iie) *value = (*value & 0x7f) | (video_->get_page2() ? 0x80 : 0x00);											break;
-								case 0xc01d:	if(is_iie) *value = (*value & 0x7f) | (video_->get_high_resolution() ? 0x80 : 0x00);								break;
-								case 0xc01e:	if(is_iie) *value = (*value & 0x7f) | (video_->get_alternative_character_set() ? 0x80 : 0x00);						break;
-								case 0xc01f:	if(is_iie) *value = (*value & 0x7f) | (video_->get_80_columns() ? 0x80 : 0x00);										break;
-								case 0xc07f:	if(is_iie) *value = (*value & 0x7f) | (video_->get_double_high_resolution() ? 0x80 : 0x00);							break;
+#define IIeSwitchRead(s)	*value = get_keyboard_input(); if(is_iie()) *value = (*value & 0x7f) | (s ? 0x80 : 0x00);
+								case 0xc011:	IIeSwitchRead(language_card_.bank1);										break;
+								case 0xc012:	IIeSwitchRead(language_card_.read);											break;
+								case 0xc013:	IIeSwitchRead(read_auxiliary_memory_);										break;
+								case 0xc014:	IIeSwitchRead(write_auxiliary_memory_);										break;
+								case 0xc015:	IIeSwitchRead(internal_CX_rom_);											break;
+								case 0xc016:	IIeSwitchRead(alternative_zero_page_);										break;
+								case 0xc017:	IIeSwitchRead(slot_C3_rom_);												break;
+								case 0xc018:	IIeSwitchRead(video_.get_80_store());										break;
+								case 0xc019:	IIeSwitchRead(video_.get_is_vertical_blank(cycles_since_video_update_));	break;
+								case 0xc01a:	IIeSwitchRead(video_.get_text());											break;
+								case 0xc01b:	IIeSwitchRead(video_.get_mixed());											break;
+								case 0xc01c:	IIeSwitchRead(video_.get_page2());											break;
+								case 0xc01d:	IIeSwitchRead(video_.get_high_resolution());								break;
+								case 0xc01e:	IIeSwitchRead(video_.get_alternative_character_set());						break;
+								case 0xc01f:	IIeSwitchRead(video_.get_80_columns());										break;
+#undef IIeSwitchRead
+
+								case 0xc07f:
+									if(is_iie()) *value = (*value & 0x7f) | (video_.get_annunciator_3() ? 0x80 : 0x00);
+								break;
 							}
 						} else {
 							// Write-only switches. All IIe as currently implemented.
-							if(is_iie) {
+							if(is_iie()) {
 								switch(address) {
-									default: printf("Write %04x?\n", address); break;
+									default: break;
 
 									case 0xc000:
 									case 0xc001:
 										update_video();
-										video_->set_80_store(!!(address&1));
+										video_.set_80_store(!!(address&1));
 										set_main_paging();
 									break;
 
@@ -564,13 +603,13 @@ template <bool is_iie> class ConcreteMachine:
 									case 0xc00c:
 									case 0xc00d:
 										update_video();
-										video_->set_80_columns(!!(address&1));
+										video_.set_80_columns(!!(address&1));
 									break;
 
 									case 0xc00e:
 									case 0xc00f:
 										update_video();
-										video_->set_alternative_character_set(!!(address&1));
+										video_.set_alternative_character_set(!!(address&1));
 									break;
 								}
 							}
@@ -589,32 +628,32 @@ template <bool is_iie> class ConcreteMachine:
 						analogue_charge_ = 0.0f;
 					} break;
 
-					/* Read-write switches. */
+					/* Switches triggered by reading or writing. */
 					case 0xc050:
 					case 0xc051:
 						update_video();
-						video_->set_text(!!(address&1));
+						video_.set_text(!!(address&1));
 					break;
-					case 0xc052:	update_video();		video_->set_mixed(false);			break;
-					case 0xc053:	update_video();		video_->set_mixed(true);			break;
+					case 0xc052:	update_video();		video_.set_mixed(false);		break;
+					case 0xc053:	update_video();		video_.set_mixed(true);			break;
 					case 0xc054:
 					case 0xc055:
 						update_video();
-						video_->set_page2(!!(address&1));
+						video_.set_page2(!!(address&1));
 						set_main_paging();
 					break;
 					case 0xc056:
 					case 0xc057:
 						update_video();
-						video_->set_high_resolution(!!(address&1));
+						video_.set_high_resolution(!!(address&1));
 						set_main_paging();
 					break;
 
 					case 0xc05e:
 					case 0xc05f:
-						if(is_iie) {
+						if(is_iie()) {
 							update_video();
-							video_->set_double_high_resolution(!(address&1));
+							video_.set_annunciator_3(!(address&1));
 						}
 					break;
 
@@ -626,12 +665,13 @@ template <bool is_iie> class ConcreteMachine:
 						}
 
 						// On the IIe, reading C010 returns additional key info.
-						if(is_iie && isReadOperation(operation)) {
+						if(is_iie() && isReadOperation(operation)) {
 							*value = (key_is_down_ ? 0x80 : 0x00) | (keyboard_input_ & 0x7f);
 						}
 					break;
 
-					case 0xc030:
+					case 0xc030: case 0xc031: case 0xc032: case 0xc033: case 0xc034: case 0xc035: case 0xc036: case 0xc037:
+					case 0xc038: case 0xc039: case 0xc03a: case 0xc03b: case 0xc03c: case 0xc03d: case 0xc03e: case 0xc03f:
 						update_audio();
 						audio_toggle_.set_output(!audio_toggle_.get_output());
 					break;
@@ -673,7 +713,7 @@ template <bool is_iie> class ConcreteMachine:
 					// If this is a card access, figure out which card is at play before determining
 					// the totality of who needs messaging.
 					size_t card_number = 0;
-					AppleII::Card::Select select = AppleII::Card::None;
+					Apple::II::Card::Select select = Apple::II::Card::None;
 
 					if(address >= 0xc100) {
 						/*
@@ -681,20 +721,20 @@ template <bool is_iie> class ConcreteMachine:
 								0xCn00 to 0xCnff: card n.
 						*/
 						card_number = (address - 0xc100) >> 8;
-						select = AppleII::Card::Device;
+						select = Apple::II::Card::Device;
 					} else {
 						/*
 							Decode the area conventionally used by cards for registers:
 								C0n0 to C0nF: card n - 8.
 						*/
 						card_number = (address - 0xc090) >> 4;
-						select = AppleII::Card::IO;
+						select = Apple::II::Card::IO;
 					}
 
 					// If the selected card is a just-in-time card, update the just-in-time cards,
 					// and then message it specifically.
 					const bool is_read = isReadOperation(operation);
-					AppleII::Card *const target = cards_[static_cast<size_t>(card_number)].get();
+					Apple::II::Card *const target = cards_[static_cast<size_t>(card_number)].get();
 					if(target && !is_every_cycle_card(target)) {
 						update_just_in_time_cards();
 						target->perform_bus_operation(select, is_read, address, value);
@@ -705,7 +745,7 @@ template <bool is_iie> class ConcreteMachine:
 					for(const auto &card: every_cycle_cards_) {
 						card->run_for(Cycles(1), is_stretched_cycle);
 						card->perform_bus_operation(
-							(card == target) ? select : AppleII::Card::None,
+							(card == target) ? select : Apple::II::Card::None,
 							is_read, address, value);
 					}
 					has_updated_cards = true;
@@ -717,7 +757,32 @@ template <bool is_iie> class ConcreteMachine:
 				const bool is_read = isReadOperation(operation);
 				for(const auto &card: every_cycle_cards_) {
 					card->run_for(Cycles(1), is_stretched_cycle);
-					card->perform_bus_operation(AppleII::Card::None, is_read, address, value);
+					card->perform_bus_operation(Apple::II::Card::None, is_read, address, value);
+				}
+			}
+
+			// Update the card lists if any mutations are due.
+			if(card_lists_are_dirty_) {
+				card_lists_are_dirty_ = false;
+
+				// There's only one counter of time since update
+				// for just-in-time cards. If something new is
+				// transitioning, that needs to be zeroed.
+				if(card_became_just_in_time_) {
+					card_became_just_in_time_ = false;
+					update_just_in_time_cards();
+				}
+
+				// Clear the two lists and repopulate.
+				every_cycle_cards_.clear();
+				just_in_time_cards_.clear();
+				for(const auto &card: cards_) {
+					if(!card) continue;
+					if(is_every_cycle_card(card.get())) {
+						every_cycle_cards_.push_back(card.get());
+					} else {
+						just_in_time_cards_.push_back(card.get());
+					}
 				}
 			}
 
@@ -763,13 +828,13 @@ template <bool is_iie> class ConcreteMachine:
 					case Key::Right:		value = 0x15;	break;
 					case Key::Down:			value = 0x0a;	break;
 					case Key::Up:			value = 0x0b;	break;
-					case Key::BackSpace:	value = 0x7f;	break;
+					case Key::Backspace:	value = 0x7f;	break;
 					default: return;
 				}
 			}
 
 			// Prior to the IIe, the keyboard could produce uppercase only.
-			if(!is_iie) value = static_cast<char>(toupper(value));
+			if(!is_iie()) value = static_cast<char>(toupper(value));
 
 			if(is_pressed) {
 				keyboard_input_ = static_cast<uint8_t>(value | 0x80);
@@ -786,7 +851,29 @@ template <bool is_iie> class ConcreteMachine:
 		}
 
 		void type_string(const std::string &string) override {
-			string_serialiser_.reset(new Utility::StringSerialiser(string, true));
+			string_serialiser_ = std::make_unique<Utility::StringSerialiser>(string, true);
+		}
+
+		// MARK:: Configuration options.
+		std::vector<std::unique_ptr<Configurable::Option>> get_options() override {
+			return Apple::II::get_options();
+		}
+
+		void set_selections(const Configurable::SelectionSet &selections_by_option) override {
+			Configurable::Display display;
+			if(Configurable::get_display(selections_by_option, display)) {
+				set_video_signal_configurable(display);
+			}
+		}
+
+		Configurable::SelectionSet get_accurate_selections() override {
+			Configurable::SelectionSet selection_set;
+			Configurable::append_display_selection(selection_set, Configurable::Display::CompositeColour);
+			return selection_set;
+		}
+
+		Configurable::SelectionSet get_user_friendly_selections() override {
+			return get_accurate_selections();
 		}
 
 		// MARK: MediaTarget
@@ -806,22 +893,25 @@ template <bool is_iie> class ConcreteMachine:
 		}
 
 		// MARK: JoystickMachine
-		std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() override {
+		const std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() override {
 			return joysticks_;
 		}
 };
 
+}
 }
 
-using namespace AppleII;
+using namespace Apple::II;
 
 Machine *Machine::AppleII(const Analyser::Static::Target *target, const ROMMachine::ROMFetcher &rom_fetcher) {
 	using Target = Analyser::Static::AppleII::Target;
 	const Target *const appleii_target = dynamic_cast<const Target *>(target);
-	if(appleii_target->model == Target::Model::IIe) {
-		return new ConcreteMachine<true>(*appleii_target, rom_fetcher);
-	} else {
-		return new ConcreteMachine<false>(*appleii_target, rom_fetcher);
+	switch(appleii_target->model) {
+		default: return nullptr;
+		case Target::Model::II: return new ConcreteMachine<Target::Model::II>(*appleii_target, rom_fetcher);
+		case Target::Model::IIplus: return new ConcreteMachine<Target::Model::IIplus>(*appleii_target, rom_fetcher);
+		case Target::Model::IIe: return new ConcreteMachine<Target::Model::IIe>(*appleii_target, rom_fetcher);
+		case Target::Model::EnhancedIIe: return new ConcreteMachine<Target::Model::EnhancedIIe>(*appleii_target, rom_fetcher);
 	}
 }
 

Machines/Apple/AppleII/AppleII.hpp

@@ -9,14 +9,18 @@
 #ifndef AppleII_hpp
 #define AppleII_hpp
 
-#include "../../Configurable/Configurable.hpp"
-#include "../../Analyser/Static/StaticAnalyser.hpp"
-#include "../ROMMachine.hpp"
+#include "../../../Configurable/Configurable.hpp"
+#include "../../../Analyser/Static/StaticAnalyser.hpp"
+#include "../../ROMMachine.hpp"
 
 #include <memory>
 #include <vector>
 
-namespace AppleII {
+namespace Apple {
+namespace II {
+
+/// @returns The options available for an Apple II.
+std::vector<std::unique_ptr<Configurable::Option>> get_options();
 
 class Machine {
 	public:
@@ -26,6 +30,7 @@ class Machine {
 		static Machine *AppleII(const Analyser::Static::Target *target, const ROMMachine::ROMFetcher &rom_fetcher);
 };
 
-};
+}
+}
 
 #endif /* AppleII_hpp */

Machines/Apple/AppleII/Card.hpp

@@ -9,11 +9,12 @@
 #ifndef Card_h
 #define Card_h
 
-#include "../../Processors/6502/6502.hpp"
-#include "../../ClockReceiver/ClockReceiver.hpp"
-#include "../../Activity/Observer.hpp"
+#include "../../../Processors/6502/6502.hpp"
+#include "../../../ClockReceiver/ClockReceiver.hpp"
+#include "../../../Activity/Observer.hpp"
 
-namespace AppleII {
+namespace Apple {
+namespace II {
 
 /*!
 	This provides a small subset of the interface offered to cards installed in
@@ -39,6 +40,7 @@ namespace AppleII {
 */
 class Card {
 	public:
+		virtual ~Card() {}
 		enum Select: int {
 			None	= 0,		// No select line is active
 			IO		= 1 << 0,	// IO select is active
@@ -81,10 +83,8 @@ class Card {
 			will receive a perform_bus_operation every cycle. To reduce the number of
 			virtual method calls, they **will not** receive run_for. run_for will propagate
 			only to cards that register for IO and/or Device accesses only.
-
-
 		*/
-		int get_select_constraints() {
+		int get_select_constraints() const {
 			return select_constraints_;
 		}
 
@@ -108,6 +108,7 @@ class Card {
 		}
 };
 
+}
 }
 
 #endif /* Card_h */

Machines/Apple/AppleII/DiskIICard.cpp

@@ -8,15 +8,25 @@
 
 #include "DiskIICard.hpp"
 
-using namespace AppleII;
+using namespace Apple::II;
 
 DiskIICard::DiskIICard(const ROMMachine::ROMFetcher &rom_fetcher, bool is_16_sector) : diskii_(2045454) {
-	const auto roms = rom_fetcher(
-		"DiskII",
-		{
-			is_16_sector ? "boot-16.rom" : "boot-13.rom",
-			is_16_sector ? "state-machine-16.rom" : "state-machine-13.rom"
+	std::vector<std::unique_ptr<std::vector<uint8_t>>> roms;
+	if(is_16_sector) {
+		roms = rom_fetcher({
+			{"DiskII", "the Disk II 16-sector boot ROM", "boot-16.rom", 256, 0xce7144f6},
+			{"DiskII", "the Disk II 16-sector state machine ROM", "state-machine-16.rom", 256, { 0x9796a238, 0xb72a2c70 } }
 		});
+	} else {
+		roms = rom_fetcher({
+			{"DiskII", "the Disk II 13-sector boot ROM", "boot-13.rom", 256, 0xd34eb2ff},
+			{"DiskII", "the Disk II 13-sector state machine ROM", "state-machine-13.rom", 256, 0x62e22620 }
+		});
+	}
+	if(!roms[0] || !roms[1]) {
+		throw ROMMachine::Error::MissingROMs;
+	}
+
 	boot_ = std::move(*roms[0]);
 	diskii_.set_state_machine(*roms[1]);
 	set_select_constraints(None);
@@ -42,7 +52,7 @@ void DiskIICard::perform_bus_operation(Select select, bool is_read, uint16_t add
 
 void DiskIICard::run_for(Cycles cycles, int stretches) {
 	if(diskii_clocking_preference_ == ClockingHint::Preference::None) return;
-	diskii_.run_for(Cycles(cycles.as_int() * 2));
+	diskii_.run_for(Cycles(cycles.as_integral() * 2));
 }
 
 void DiskIICard::set_disk(const std::shared_ptr<Storage::Disk::Disk> &disk, int drive) {
@@ -55,7 +65,7 @@ void DiskIICard::set_activity_observer(Activity::Observer *observer) {
 
 void DiskIICard::set_component_prefers_clocking(ClockingHint::Source *component, ClockingHint::Preference preference) {
 	diskii_clocking_preference_ = preference;
-	set_select_constraints((preference != ClockingHint::Preference::RealTime) ? (IO | Device) : 0);
+	set_select_constraints((preference != ClockingHint::Preference::RealTime) ? (IO | Device) : None);
 }
 
 Storage::Disk::Drive &DiskIICard::get_drive(int drive) {

Machines/Apple/AppleII/DiskIICard.hpp

@@ -10,17 +10,18 @@
 #define DiskIICard_hpp
 
 #include "Card.hpp"
-#include "../ROMMachine.hpp"
+#include "../../ROMMachine.hpp"
 
-#include "../../Components/DiskII/DiskII.hpp"
-#include "../../Storage/Disk/Disk.hpp"
-#include "../../ClockReceiver/ClockingHintSource.hpp"
+#include "../../../Components/DiskII/DiskII.hpp"
+#include "../../../Storage/Disk/Disk.hpp"
+#include "../../../ClockReceiver/ClockingHintSource.hpp"
 
 #include <cstdint>
 #include <memory>
 #include <vector>
 
-namespace AppleII {
+namespace Apple {
+namespace II {
 
 class DiskIICard: public Card, public ClockingHint::Observer {
 	public:
@@ -41,6 +42,7 @@ class DiskIICard: public Card, public ClockingHint::Observer {
 		ClockingHint::Preference diskii_clocking_preference_ = ClockingHint::Preference::RealTime;
 };
 
+}
 }
 
 #endif /* DiskIICard_hpp */

Machines/Apple/AppleII/Video.cpp

@@ -0,0 +1,340 @@
+//
+//  Video.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 14/04/2018.
+//  Copyright 2018 Thomas Harte. All rights reserved.
+//
+
+#include "Video.hpp"
+
+using namespace Apple::II::Video;
+
+VideoBase::VideoBase(bool is_iie, std::function<void(Cycles)> &&target) :
+	crt_(910, 1, Outputs::Display::Type::NTSC60, Outputs::Display::InputDataType::Luminance1),
+	is_iie_(is_iie),
+	deferrer_(std::move(target)) {
+
+	// Show only the centre 75% of the TV frame.
+	crt_.set_display_type(Outputs::Display::DisplayType::CompositeColour);
+	crt_.set_visible_area(Outputs::Display::Rect(0.118f, 0.122f, 0.77f, 0.77f));
+
+	// TODO: there seems to be some sort of bug whereby switching modes can cause
+	// a signal discontinuity that knocks phase out of whack. So it isn't safe to
+	// use default_colour_bursts elsewhere, though it otherwise should be. If/when
+	// it is, start doing so and return to setting the immediate phase up here.
+//	crt_.set_immediate_default_phase(0.5f);
+
+	character_zones[0].xor_mask = 0;
+	character_zones[0].address_mask = 0x3f;
+	character_zones[1].xor_mask = 0;
+	character_zones[1].address_mask = 0x3f;
+	character_zones[2].xor_mask = 0;
+	character_zones[2].address_mask = 0x3f;
+	character_zones[3].xor_mask = 0;
+	character_zones[3].address_mask = 0x3f;
+
+	if(is_iie) {
+		character_zones[0].xor_mask =
+		character_zones[2].xor_mask =
+		character_zones[3].xor_mask = 0xff;
+		character_zones[2].address_mask =
+		character_zones[3].address_mask = 0xff;
+	}
+}
+
+void VideoBase::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
+	crt_.set_scan_target(scan_target);
+}
+
+void VideoBase::set_display_type(Outputs::Display::DisplayType display_type) {
+	crt_.set_display_type(display_type);
+}
+
+/*
+	Rote setters and getters.
+*/
+void VideoBase::set_alternative_character_set(bool alternative_character_set) {
+	set_alternative_character_set_ = alternative_character_set;
+	deferrer_.defer(Cycles(2), [=] {
+		alternative_character_set_ = alternative_character_set;
+		if(alternative_character_set) {
+			character_zones[1].address_mask = 0xff;
+			character_zones[1].xor_mask = 0;
+		} else {
+			character_zones[1].address_mask = 0x3f;
+			character_zones[1].xor_mask = flash_mask();
+		}
+	});
+}
+
+bool VideoBase::get_alternative_character_set() {
+	return set_alternative_character_set_;
+}
+
+void VideoBase::set_80_columns(bool columns_80) {
+	set_columns_80_ = columns_80;
+	deferrer_.defer(Cycles(2), [=] {
+		columns_80_ = columns_80;
+	});
+}
+
+bool VideoBase::get_80_columns() {
+	return set_columns_80_;
+}
+
+void VideoBase::set_80_store(bool store_80) {
+	set_store_80_ = store_80_ = store_80;
+}
+
+bool VideoBase::get_80_store() {
+	return set_store_80_;
+}
+
+void VideoBase::set_page2(bool page2) {
+	set_page2_ = page2_ = page2;
+}
+
+bool VideoBase::get_page2() {
+	return set_page2_;
+}
+
+void VideoBase::set_text(bool text) {
+	set_text_ = text;
+	deferrer_.defer(Cycles(2), [=] {
+		text_ = text;
+	});
+}
+
+bool VideoBase::get_text() {
+	return set_text_;
+}
+
+void VideoBase::set_mixed(bool mixed) {
+	set_mixed_ = mixed;
+	deferrer_.defer(Cycles(2), [=] {
+		mixed_ = mixed;
+	});
+}
+
+bool VideoBase::get_mixed() {
+	return set_mixed_;
+}
+
+void VideoBase::set_high_resolution(bool high_resolution) {
+	set_high_resolution_ = high_resolution;
+	deferrer_.defer(Cycles(2), [=] {
+		high_resolution_ = high_resolution;
+	});
+}
+
+bool VideoBase::get_high_resolution() {
+	return set_high_resolution_;
+}
+
+void VideoBase::set_annunciator_3(bool annunciator_3) {
+	set_annunciator_3_ = annunciator_3;
+	deferrer_.defer(Cycles(2), [=] {
+		annunciator_3_ = annunciator_3;
+		high_resolution_mask_ = annunciator_3_ ? 0x7f : 0xff;
+	});
+}
+
+bool VideoBase::get_annunciator_3() {
+	return set_annunciator_3_;
+}
+
+void VideoBase::set_character_rom(const std::vector<uint8_t> &character_rom) {
+	character_rom_ = character_rom;
+
+	// Flip all character contents based on the second line of the $ graphic.
+	if(character_rom_[0x121] == 0x3c || character_rom_[0x122] == 0x3c) {
+		for(auto &graphic : character_rom_) {
+			graphic =
+				((graphic & 0x01) ? 0x40 : 0x00) |
+				((graphic & 0x02) ? 0x20 : 0x00) |
+				((graphic & 0x04) ? 0x10 : 0x00) |
+				((graphic & 0x08) ? 0x08 : 0x00) |
+				((graphic & 0x10) ? 0x04 : 0x00) |
+				((graphic & 0x20) ? 0x02 : 0x00) |
+				((graphic & 0x40) ? 0x01 : 0x00);
+		}
+	}
+}
+
+void VideoBase::output_text(uint8_t *target, const uint8_t *const source, size_t length, size_t pixel_row) const {
+	for(size_t c = 0; c < length; ++c) {
+		const int character = source[c] & character_zones[source[c] >> 6].address_mask;
+		const uint8_t xor_mask = character_zones[source[c] >> 6].xor_mask;
+		const std::size_t character_address = static_cast<std::size_t>(character << 3) + pixel_row;
+		const uint8_t character_pattern = character_rom_[character_address] ^ xor_mask;
+
+		// The character ROM is output MSB to LSB rather than LSB to MSB.
+		target[0] = target[1] = character_pattern & 0x40;
+		target[2] = target[3] = character_pattern & 0x20;
+		target[4] = target[5] = character_pattern & 0x10;
+		target[6] = target[7] = character_pattern & 0x08;
+		target[8] = target[9] = character_pattern & 0x04;
+		target[10] = target[11] = character_pattern & 0x02;
+		target[12] = target[13] = character_pattern & 0x01;
+		graphics_carry_ = character_pattern & 0x01;
+		target += 14;
+	}
+}
+
+void VideoBase::output_double_text(uint8_t *target, const uint8_t *const source, const uint8_t *const auxiliary_source, size_t length, size_t pixel_row) const {
+	for(size_t c = 0; c < length; ++c) {
+		const std::size_t character_addresses[2] = {
+			static_cast<std::size_t>(
+				(auxiliary_source[c] & character_zones[auxiliary_source[c] >> 6].address_mask) << 3
+			) + pixel_row,
+			static_cast<std::size_t>(
+				(source[c] & character_zones[source[c] >> 6].address_mask) << 3
+			) + pixel_row
+		};
+
+		const uint8_t character_patterns[2] = {
+			static_cast<uint8_t>(
+				character_rom_[character_addresses[0]] ^ character_zones[auxiliary_source[c] >> 6].xor_mask
+			),
+			static_cast<uint8_t>(
+				character_rom_[character_addresses[1]] ^ character_zones[source[c] >> 6].xor_mask
+			)
+		};
+
+		// The character ROM is output MSB to LSB rather than LSB to MSB.
+		target[0] = character_patterns[0] & 0x40;
+		target[1] = character_patterns[0] & 0x20;
+		target[2] = character_patterns[0] & 0x10;
+		target[3] = character_patterns[0] & 0x08;
+		target[4] = character_patterns[0] & 0x04;
+		target[5] = character_patterns[0] & 0x02;
+		target[6] = character_patterns[0] & 0x01;
+		target[7] = character_patterns[1] & 0x40;
+		target[8] = character_patterns[1] & 0x20;
+		target[9] = character_patterns[1] & 0x10;
+		target[10] = character_patterns[1] & 0x08;
+		target[11] = character_patterns[1] & 0x04;
+		target[12] = character_patterns[1] & 0x02;
+		target[13] = character_patterns[1] & 0x01;
+		graphics_carry_ = character_patterns[1] & 0x01;
+		target += 14;
+	}
+}
+
+void VideoBase::output_low_resolution(uint8_t *target, const uint8_t *const source, size_t length, int column, int row) const {
+	const int row_shift = row&4;
+	for(size_t c = 0; c < length; ++c) {
+		// Low-resolution graphics mode shifts the colour code on a loop, but has to account for whether this
+		// 14-sample output window is starting at the beginning of a colour cycle or halfway through.
+		if((column + static_cast<int>(c))&1) {
+			target[0] = target[4] = target[8] = target[12] = (source[c] >> row_shift) & 4;
+			target[1] = target[5] = target[9] = target[13] = (source[c] >> row_shift) & 8;
+			target[2] = target[6] = target[10] = (source[c] >> row_shift) & 1;
+			target[3] = target[7] = target[11] = (source[c] >> row_shift) & 2;
+			graphics_carry_ = (source[c] >> row_shift) & 8;
+		} else {
+			target[0] = target[4] = target[8] = target[12] = (source[c] >> row_shift) & 1;
+			target[1] = target[5] = target[9] = target[13] = (source[c] >> row_shift) & 2;
+			target[2] = target[6] = target[10] = (source[c] >> row_shift) & 4;
+			target[3] = target[7] = target[11] = (source[c] >> row_shift) & 8;
+			graphics_carry_ = (source[c] >> row_shift) & 2;
+		}
+		target += 14;
+	}
+}
+
+void VideoBase::output_fat_low_resolution(uint8_t *target, const uint8_t *const source, size_t length, int column, int row) const {
+	const int row_shift = row&4;
+	for(size_t c = 0; c < length; ++c) {
+		// Fat low-resolution mode appears not to do anything to try to make odd and
+		// even columns compatible.
+		target[0] = target[1] = target[8] = target[9] = (source[c] >> row_shift) & 1;
+		target[2] = target[3] = target[10] = target[11] = (source[c] >> row_shift) & 2;
+		target[4] = target[5] = target[12] = target[13] = (source[c] >> row_shift) & 4;
+		target[6] = target[7] = (source[c] >> row_shift) & 8;
+		graphics_carry_ = (source[c] >> row_shift) & 4;
+		target += 14;
+	}
+}
+
+void VideoBase::output_double_low_resolution(uint8_t *target, const uint8_t *const source, const uint8_t *const auxiliary_source, size_t length, int column, int row) const {
+	const int row_shift = row&4;
+	for(size_t c = 0; c < length; ++c) {
+		if((column + static_cast<int>(c))&1) {
+			target[0] = target[4] = (auxiliary_source[c] >> row_shift) & 2;
+			target[1] = target[5] = (auxiliary_source[c] >> row_shift) & 4;
+			target[2] = target[6] = (auxiliary_source[c] >> row_shift) & 8;
+			target[3] = (auxiliary_source[c] >> row_shift) & 1;
+
+			target[8] = target[12] = (source[c] >> row_shift) & 4;
+			target[9] = target[13] = (source[c] >> row_shift) & 8;
+			target[10] = (source[c] >> row_shift) & 1;
+			target[7] = target[11] = (source[c] >> row_shift) & 2;
+			graphics_carry_ = (source[c] >> row_shift) & 8;
+		} else {
+			target[0] = target[4] = (auxiliary_source[c] >> row_shift) & 8;
+			target[1] = target[5] = (auxiliary_source[c] >> row_shift) & 1;
+			target[2] = target[6] = (auxiliary_source[c] >> row_shift) & 2;
+			target[3] = (auxiliary_source[c] >> row_shift) & 4;
+
+			target[8] = target[12] = (source[c] >> row_shift) & 1;
+			target[9] = target[13] = (source[c] >> row_shift) & 2;
+			target[10] = (source[c] >> row_shift) & 4;
+			target[7] = target[11] = (source[c] >> row_shift) & 8;
+			graphics_carry_ = (source[c] >> row_shift) & 2;
+		}
+		target += 14;
+	}
+}
+
+void VideoBase::output_high_resolution(uint8_t *target, const uint8_t *const source, size_t length) const {
+	for(size_t c = 0; c < length; ++c) {
+		// High resolution graphics shift out LSB to MSB, optionally with a delay of half a pixel.
+		// If there is a delay, the previous output level is held to bridge the gap.
+		// Delays may be ignored on a IIe if Annunciator 3 is set; that's the state that
+		// high_resolution_mask_ models.
+		if(source[c] & high_resolution_mask_ & 0x80) {
+			target[0] = graphics_carry_;
+			target[1] = target[2] = source[c] & 0x01;
+			target[3] = target[4] = source[c] & 0x02;
+			target[5] = target[6] = source[c] & 0x04;
+			target[7] = target[8] = source[c] & 0x08;
+			target[9] = target[10] = source[c] & 0x10;
+			target[11] = target[12] = source[c] & 0x20;
+			target[13] = source[c] & 0x40;
+		} else {
+			target[0] = target[1] = source[c] & 0x01;
+			target[2] = target[3] = source[c] & 0x02;
+			target[4] = target[5] = source[c] & 0x04;
+			target[6] = target[7] = source[c] & 0x08;
+			target[8] = target[9] = source[c] & 0x10;
+			target[10] = target[11] = source[c] & 0x20;
+			target[12] = target[13] = source[c] & 0x40;
+		}
+		graphics_carry_ = source[c] & 0x40;
+		target += 14;
+	}
+}
+
+void VideoBase::output_double_high_resolution(uint8_t *target, const uint8_t *const source, const uint8_t *const auxiliary_source, size_t length) const {
+	for(size_t c = 0; c < length; ++c) {
+		target[0] = auxiliary_source[c] & 0x01;
+		target[1] = auxiliary_source[c] & 0x02;
+		target[2] = auxiliary_source[c] & 0x04;
+		target[3] = auxiliary_source[c] & 0x08;
+		target[4] = auxiliary_source[c] & 0x10;
+		target[5] = auxiliary_source[c] & 0x20;
+		target[6] = auxiliary_source[c] & 0x40;
+		target[7] = source[c] & 0x01;
+		target[8] = source[c] & 0x02;
+		target[9] = source[c] & 0x04;
+		target[10] = source[c] & 0x08;
+		target[11] = source[c] & 0x10;
+		target[12] = source[c] & 0x20;
+		target[13] = source[c] & 0x40;
+
+		graphics_carry_ = auxiliary_source[c] & 0x40;
+		target += 14;
+	}
+}

Machines/Apple/AppleII/Video.hpp

@@ -0,0 +1,608 @@
+//
+//  Video.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 14/04/2018.
+//  Copyright 2018 Thomas Harte. All rights reserved.
+//
+
+#ifndef Video_hpp
+#define Video_hpp
+
+#include "../../../Outputs/CRT/CRT.hpp"
+#include "../../../ClockReceiver/ClockReceiver.hpp"
+#include "../../../ClockReceiver/DeferredQueue.hpp"
+
+#include <array>
+#include <vector>
+
+namespace Apple {
+namespace II {
+namespace Video {
+
+class BusHandler {
+	public:
+		/*!
+			Requests fetching of the @c count bytes starting from @c address.
+
+			The handler should write the values from base memory to @c base_target, and those
+			from auxiliary memory to @c auxiliary_target. If the machine has no axiliary memory,
+			it needn't write anything to auxiliary_target.
+		*/
+		void perform_read(uint16_t address, size_t count, uint8_t *base_target, uint8_t *auxiliary_target) {
+		}
+};
+
+class VideoBase {
+	public:
+		VideoBase(bool is_iie, std::function<void(Cycles)> &&target);
+
+		/// Sets the scan target.
+		void set_scan_target(Outputs::Display::ScanTarget *scan_target);
+
+		/// Sets the type of output.
+		void set_display_type(Outputs::Display::DisplayType);
+
+		/*
+			Descriptions for the setters below are taken verbatim from
+			the Apple IIe Technical Reference. Addresses are the conventional
+			locations within the Apple II memory map. Only those which affect
+			video output are implemented here.
+
+			Those registers which don't exist on a II/II+ are marked.
+		*/
+
+		/*!
+			Setter for ALTCHAR ($C00E/$C00F; triggers on write only):
+
+			* Off: display text using primary character set.
+			* On: display text using alternate character set.
+
+			Doesn't exist on a II/II+.
+		*/
+		void set_alternative_character_set(bool);
+		bool get_alternative_character_set();
+
+		/*!
+			Setter for 80COL ($C00C/$C00D; triggers on write only).
+
+			* Off: display 40 columns.
+			* On: display 80 columns.
+
+			Doesn't exist on a II/II+.
+		*/
+		void set_80_columns(bool);
+		bool get_80_columns();
+
+		/*!
+			Setter for 80STORE ($C000/$C001; triggers on write only).
+
+			* Off: cause PAGE2 to select auxiliary RAM.
+			* On: cause PAGE2 to switch main RAM areas.
+
+			Doesn't exist on a II/II+.
+		*/
+		void set_80_store(bool);
+		bool get_80_store();
+
+		/*!
+			Setter for PAGE2 ($C054/$C055; triggers on read or write).
+
+			* Off: select Page 1.
+			* On: select Page 2 or, if 80STORE on, Page 1 in auxiliary memory.
+
+			80STORE doesn't exist on a II/II+; therefore this always selects
+			either Page 1 or Page 2 on those machines.
+		*/
+		void set_page2(bool);
+		bool get_page2();
+
+		/*!
+			Setter for TEXT ($C050/$C051; triggers on read or write).
+
+			* Off: display graphics or, if MIXED on, mixed.
+			* On: display text.
+		*/
+		void set_text(bool);
+		bool get_text();
+
+		/*!
+			Setter for MIXED ($C052/$C053; triggers on read or write).
+
+			* Off: display only text or only graphics.
+			* On: if TEXT off, display text and graphics.
+		*/
+		void set_mixed(bool);
+		bool get_mixed();
+
+		/*!
+			Setter for HIRES ($C056/$C057; triggers on read or write).
+
+			* Off: if TEXT off, display low-resolution graphics.
+			* On: if TEXT off, display high-resolution or, if DHIRES on, double high-resolution graphics.
+
+			DHIRES doesn't exist on a II/II+; therefore this always selects
+			either high- or low-resolution graphics on those machines.
+
+			Despite Apple's documentation, the IIe also supports double low-resolution
+			graphics, which are the 80-column analogue to ordinary low-resolution 40-column
+			low-resolution graphics.
+		*/
+		void set_high_resolution(bool);
+		bool get_high_resolution();
+
+		/*!
+			Setter for annunciator 3.
+
+			* On: turn on annunciator 3.
+			* Off: turn off annunciator 3.
+
+			This exists on both the II/II+ and the IIe, but has no effect on
+			video on the older machines. It's intended to be used on the IIe
+			to confirm double-high resolution mode but has side effects in
+			selecting mixed mode output and discarding high-resolution
+			delay bits.
+		*/
+		void set_annunciator_3(bool);
+		bool get_annunciator_3();
+
+		// Setup for text mode.
+		void set_character_rom(const std::vector<uint8_t> &);
+
+	protected:
+		Outputs::CRT::CRT crt_;
+
+		// State affecting output video stream generation.
+		uint8_t *pixel_pointer_ = nullptr;
+
+		// State affecting logical state.
+		int row_ = 0, column_ = 0, flash_ = 0;
+		uint8_t flash_mask() {
+			return static_cast<uint8_t>((flash_ / flash_length) * 0xff);
+		}
+
+		// Enumerates all Apple II and IIe display modes.
+		enum class GraphicsMode {
+			Text = 0,
+			DoubleText,
+			HighRes,
+			DoubleHighRes,
+			LowRes,
+			DoubleLowRes,
+			FatLowRes
+		};
+		bool is_text_mode(GraphicsMode m) { return m <= GraphicsMode::DoubleText; }
+		bool is_double_mode(GraphicsMode m) { return !!(static_cast<int>(m)&1); }
+
+		// Various soft-switch values.
+		bool alternative_character_set_ = false, set_alternative_character_set_ = false;
+		bool columns_80_ = false, set_columns_80_ = false;
+		bool store_80_ = false, set_store_80_ = false;
+		bool page2_ = false, set_page2_ = false;
+		bool text_ = true, set_text_ = true;
+		bool mixed_ = false, set_mixed_ = false;
+		bool high_resolution_ = false, set_high_resolution_ = false;
+		bool annunciator_3_ = false, set_annunciator_3_ = false;
+
+		// Graphics carry is the final level output in a fetch window;
+		// it carries on into the next if it's high resolution with
+		// the delay bit set.
+		mutable uint8_t graphics_carry_ = 0;
+		bool was_double_ = false;
+		uint8_t high_resolution_mask_ = 0xff;
+
+		// This holds a copy of the character ROM. The regular character
+		// set is assumed to be in the first 64*8 bytes; the alternative
+		// is in the 128*8 bytes after that.
+		std::vector<uint8_t> character_rom_;
+
+		// Memory is fetched ahead of time into this array;
+		// this permits the correct delay between fetching
+		// without having to worry about a rolling buffer.
+		std::array<uint8_t, 40> base_stream_;
+		std::array<uint8_t, 40> auxiliary_stream_;
+
+		bool is_iie_ = false;
+		static constexpr int flash_length = 8406;
+
+		// Describes the current text mode mapping from in-memory character index
+		// to output character.
+		struct CharacterMapping {
+			uint8_t address_mask;
+			uint8_t xor_mask;
+		};
+		CharacterMapping character_zones[4];
+
+		/*!
+			Outputs 40-column text to @c target, using @c length bytes from @c source.
+		*/
+		void output_text(uint8_t *target, const uint8_t *source, size_t length, size_t pixel_row) const;
+
+		/*!
+			Outputs 80-column text to @c target, drawing @c length columns from @c source and @c auxiliary_source.
+		*/
+		void output_double_text(uint8_t *target, const uint8_t *source, const uint8_t *auxiliary_source, size_t length, size_t pixel_row) const;
+
+		/*!
+			Outputs 40-column low-resolution graphics to @c target, drawing @c length columns from @c source.
+		*/
+		void output_low_resolution(uint8_t *target, const uint8_t *source, size_t length, int column, int row) const;
+
+		/*!
+			Outputs 80-column low-resolution graphics to @c target, drawing @c length columns from @c source and @c auxiliary_source.
+		*/
+		void output_double_low_resolution(uint8_t *target, const uint8_t *source, const uint8_t *auxiliary_source, size_t length, int column, int row) const;
+
+		/*!
+			Outputs 40-column high-resolution graphics to @c target, drawing @c length columns from @c source.
+		*/
+		void output_high_resolution(uint8_t *target, const uint8_t *source, size_t length) const;
+
+		/*!
+			Outputs 80-column double-high-resolution graphics to @c target, drawing @c length columns from @c source.
+		*/
+		void output_double_high_resolution(uint8_t *target, const uint8_t *source, const uint8_t *auxiliary_source, size_t length) const;
+
+		/*!
+			Outputs 40-column "fat low resolution" graphics to @c target, drawing @c length columns from @c source.
+
+			Fat low-resolution mode is like regular low-resolution mode except that data is shifted out on the 7M
+			clock rather than the 14M.
+		*/
+		void output_fat_low_resolution(uint8_t *target, const uint8_t *source, size_t length, int column, int row) const;
+
+		// Maintain a DeferredQueue for delayed mode switches.
+		DeferredQueue<Cycles> deferrer_;
+};
+
+template <class BusHandler, bool is_iie> class Video: public VideoBase {
+	public:
+		/// Constructs an instance of the video feed; a CRT is also created.
+		Video(BusHandler &bus_handler) :
+			VideoBase(is_iie, [=] (Cycles cycles) { advance(cycles); }),
+			bus_handler_(bus_handler) {}
+
+		/*!
+			Runs video for @c cycles.
+		*/
+		void run_for(Cycles cycles) {
+			deferrer_.run_for(cycles);
+		}
+
+		/*!
+			Obtains the last value the video read prior to time now+offset.
+		*/
+		uint8_t get_last_read_value(Cycles offset) {
+			// Rules of generation:
+			// (1)	a complete sixty-five-cycle scan line consists of sixty-five consecutive bytes of
+			//		display buffer memory that starts twenty-five bytes prior to the actual data to be displayed.
+			// (2)	During VBL the data acts just as if it were starting a whole new frame from the beginning, but
+			//		it never finishes this pseudo-frame. After getting one third of the way through the frame (to
+			//		scan line $3F), it suddenly repeats the previous six scan lines ($3A through $3F) before aborting
+			//		to begin the next true frame.
+			//
+			// Source: Have an Apple Split by Bob Bishop; http://rich12345.tripod.com/aiivideo/softalk.html
+
+			// Determine column at offset.
+			int mapped_column = column_ + int(offset.as_integral());
+
+			// Map that backwards from the internal pixels-at-start generation to pixels-at-end
+			// (so what was column 0 is now column 25).
+			mapped_column += 25;
+
+			// Apply carry into the row counter.
+			int mapped_row = row_ + (mapped_column / 65);
+			mapped_column %= 65;
+			mapped_row %= 262;
+
+			// Apple out-of-bounds row logic.
+			if(mapped_row >= 256) {
+				mapped_row = 0x3a + (mapped_row&255);
+			} else {
+				mapped_row %= 192;
+			}
+
+			// Calculate the address and return the value.
+			uint16_t read_address = static_cast<uint16_t>(get_row_address(mapped_row) + mapped_column - 25);
+			uint8_t value, aux_value;
+			bus_handler_.perform_read(read_address, 1, &value, &aux_value);
+			return value;
+		}
+
+		/*!
+			@returns @c true if the display will be within vertical blank at now + @c offset; @c false otherwise.
+		*/
+		bool get_is_vertical_blank(Cycles offset) {
+			// Map that backwards from the internal pixels-at-start generation to pixels-at-end
+			// (so what was column 0 is now column 25).
+			int mapped_column = column_ + int(offset.as_integral());
+
+			// Map that backwards from the internal pixels-at-start generation to pixels-at-end
+			// (so what was column 0 is now column 25).
+			mapped_column += 25;
+
+			// Apply carry into the row counter and test it for location.
+			int mapped_row = row_ + (mapped_column / 65);
+			return (mapped_row % 262) >= 192;
+		}
+
+	private:
+		/*!
+			Advances time by @c cycles; expects to be fed by the CPU clock.
+			Implicitly adds an extra half a colour clock at the end of
+			line.
+		*/
+		void advance(Cycles cycles) {
+			/*
+				Addressing scheme used throughout is that column 0 is the first column with pixels in it;
+				row 0 is the first row with pixels in it.
+
+				A frame is oriented around 65 cycles across, 262 lines down.
+			*/
+			constexpr int first_sync_line = 220;		// A complete guess. Information needed.
+			constexpr int first_sync_column = 49;	// Also a guess.
+			constexpr int sync_length = 4;			// One of the two likely candidates.
+
+			int int_cycles = int(cycles.as_integral());
+			while(int_cycles) {
+				const int cycles_this_line = std::min(65 - column_, int_cycles);
+				const int ending_column = column_ + cycles_this_line;
+				const bool is_vertical_sync_line = (row_ >= first_sync_line && row_ < first_sync_line + 3);
+
+				if(is_vertical_sync_line) {
+					// In effect apply an XOR to HSYNC and VSYNC flags in order to include equalising
+					// pulses (and hencce keep hsync approximately where it should be during vsync).
+					const int blank_start = std::max(first_sync_column - sync_length, column_);
+					const int blank_end = std::min(first_sync_column, ending_column);
+					if(blank_end > blank_start) {
+						if(blank_start > column_) {
+							crt_.output_sync((blank_start - column_) * 14);
+						}
+						crt_.output_blank((blank_end - blank_start) * 14);
+						if(blank_end < ending_column) {
+							crt_.output_sync((ending_column - blank_end) * 14);
+						}
+					} else {
+						crt_.output_sync(cycles_this_line * 14);
+					}
+				} else {
+					const GraphicsMode line_mode = graphics_mode(row_);
+
+					// Determine whether there's any fetching to do. Fetching occurs during the first
+					// 40 columns of rows prior to 192.
+					if(row_ < 192 && column_ < 40) {
+						const int character_row = row_ >> 3;
+						const uint16_t row_address = static_cast<uint16_t>((character_row >> 3) * 40 + ((character_row&7) << 7));
+
+						// Grab the memory contents that'll be needed momentarily.
+						const int fetch_end = std::min(40, ending_column);
+						uint16_t fetch_address;
+						switch(line_mode) {
+							default:
+							case GraphicsMode::Text:
+							case GraphicsMode::DoubleText:
+							case GraphicsMode::LowRes:
+							case GraphicsMode::FatLowRes:
+							case GraphicsMode::DoubleLowRes: {
+								const uint16_t text_address = static_cast<uint16_t>(((video_page()+1) * 0x400) + row_address);
+								fetch_address = static_cast<uint16_t>(text_address + column_);
+							} break;
+
+							case GraphicsMode::HighRes:
+							case GraphicsMode::DoubleHighRes:
+								fetch_address = static_cast<uint16_t>(((video_page()+1) * 0x2000) + row_address + ((row_&7) << 10) + column_);
+							break;
+						}
+
+						bus_handler_.perform_read(
+							fetch_address,
+							static_cast<size_t>(fetch_end - column_),
+							&base_stream_[static_cast<size_t>(column_)],
+							&auxiliary_stream_[static_cast<size_t>(column_)]);
+					}
+
+					if(row_ < 192) {
+						// The pixel area is the first 40.5 columns; base contents
+						// remain where they would naturally be but auxiliary
+						// graphics appear to the left of that.
+						if(!column_) {
+							pixel_pointer_ = crt_.begin_data(568);
+							graphics_carry_ = 0;
+							was_double_ = true;
+						}
+
+						if(column_ < 40) {
+							const int pixel_start = std::max(0, column_);
+							const int pixel_end = std::min(40, ending_column);
+							const int pixel_row = row_ & 7;
+
+							const bool is_double = Video::is_double_mode(line_mode);
+							if(!is_double && was_double_ && pixel_pointer_) {
+								pixel_pointer_[pixel_start*14 + 0] =
+								pixel_pointer_[pixel_start*14 + 1] =
+								pixel_pointer_[pixel_start*14 + 2] =
+								pixel_pointer_[pixel_start*14 + 3] =
+								pixel_pointer_[pixel_start*14 + 4] =
+								pixel_pointer_[pixel_start*14 + 5] =
+								pixel_pointer_[pixel_start*14 + 6] = 0;
+							}
+							was_double_ = is_double;
+
+							if(pixel_pointer_) {
+								switch(line_mode) {
+									case GraphicsMode::Text:
+										output_text(
+											&pixel_pointer_[pixel_start * 14 + 7],
+											&base_stream_[static_cast<size_t>(pixel_start)],
+											static_cast<size_t>(pixel_end - pixel_start),
+											static_cast<size_t>(pixel_row));
+									break;
+
+									case GraphicsMode::DoubleText:
+										output_double_text(
+											&pixel_pointer_[pixel_start * 14],
+											&base_stream_[static_cast<size_t>(pixel_start)],
+											&auxiliary_stream_[static_cast<size_t>(pixel_start)],
+											static_cast<size_t>(pixel_end - pixel_start),
+											static_cast<size_t>(pixel_row));
+									break;
+
+									case GraphicsMode::LowRes:
+										output_low_resolution(
+											&pixel_pointer_[pixel_start * 14 + 7],
+											&base_stream_[static_cast<size_t>(pixel_start)],
+											static_cast<size_t>(pixel_end - pixel_start),
+											pixel_start,
+											pixel_row);
+									break;
+
+									case GraphicsMode::FatLowRes:
+										output_fat_low_resolution(
+											&pixel_pointer_[pixel_start * 14 + 7],
+											&base_stream_[static_cast<size_t>(pixel_start)],
+											static_cast<size_t>(pixel_end - pixel_start),
+											pixel_start,
+											pixel_row);
+									break;
+
+									case GraphicsMode::DoubleLowRes:
+										output_double_low_resolution(
+											&pixel_pointer_[pixel_start * 14],
+											&base_stream_[static_cast<size_t>(pixel_start)],
+											&auxiliary_stream_[static_cast<size_t>(pixel_start)],
+											static_cast<size_t>(pixel_end - pixel_start),
+											pixel_start,
+											pixel_row);
+									break;
+
+									case GraphicsMode::HighRes:
+										output_high_resolution(
+											&pixel_pointer_[pixel_start * 14 + 7],
+											&base_stream_[static_cast<size_t>(pixel_start)],
+											static_cast<size_t>(pixel_end - pixel_start));
+									break;
+
+									case GraphicsMode::DoubleHighRes:
+										output_double_high_resolution(
+											&pixel_pointer_[pixel_start * 14],
+											&base_stream_[static_cast<size_t>(pixel_start)],
+											&auxiliary_stream_[static_cast<size_t>(pixel_start)],
+											static_cast<size_t>(pixel_end - pixel_start));
+									break;
+
+									default: break;
+								}
+							}
+
+							if(pixel_end == 40) {
+								if(pixel_pointer_) {
+									if(was_double_) {
+										pixel_pointer_[560] = pixel_pointer_[561] = pixel_pointer_[562] = pixel_pointer_[563] =
+										pixel_pointer_[564] = pixel_pointer_[565] = pixel_pointer_[566] = pixel_pointer_[567] = 0;
+									} else {
+										if(line_mode == GraphicsMode::HighRes && base_stream_[39]&0x80)
+											pixel_pointer_[567] = graphics_carry_;
+										else
+											pixel_pointer_[567] = 0;
+									}
+								}
+
+								crt_.output_data(568, 568);
+								pixel_pointer_ = nullptr;
+							}
+						}
+					} else {
+						if(column_ < 40 && ending_column >= 40) {
+							crt_.output_blank(568);
+						}
+					}
+
+					/*
+						The left border, sync, right border pattern doesn't depend on whether
+						there were pixels this row and is output as soon as it is known.
+					*/
+
+					if(column_ < first_sync_column && ending_column >= first_sync_column) {
+						crt_.output_blank(first_sync_column*14 - 568);
+					}
+
+					if(column_ < (first_sync_column + sync_length) && ending_column >= (first_sync_column + sync_length)) {
+						crt_.output_sync(sync_length*14);
+					}
+
+					int second_blank_start;
+					if(!is_text_mode(graphics_mode(row_+1))) {
+						const int colour_burst_start = std::max(first_sync_column + sync_length + 1, column_);
+						const int colour_burst_end = std::min(first_sync_column + sync_length + 4, ending_column);
+						if(colour_burst_end > colour_burst_start) {
+							crt_.output_colour_burst((colour_burst_end - colour_burst_start) * 14, 0);
+						}
+
+						second_blank_start = std::max(first_sync_column + sync_length + 3, column_);
+					} else {
+						second_blank_start = std::max(first_sync_column + sync_length, column_);
+					}
+
+					if(ending_column > second_blank_start) {
+						crt_.output_blank((ending_column - second_blank_start) * 14);
+					}
+				}
+
+				int_cycles -= cycles_this_line;
+				column_ = (column_ + cycles_this_line) % 65;
+				if(!column_) {
+					row_ = (row_ + 1) % 262;
+					flash_ = (flash_ + 1) % (2 * flash_length);
+					if(!alternative_character_set_) {
+						character_zones[1].xor_mask = flash_mask();
+					}
+
+					// Add an extra half a colour cycle of blank; this isn't counted in the run_for
+					// count explicitly but is promised. If this is a vertical sync line, output sync
+					// instead of blank, taking that to be the default level.
+					if(is_vertical_sync_line) {
+						crt_.output_sync(2);
+					} else {
+						crt_.output_blank(2);
+					}
+				}
+			}
+		}
+
+		GraphicsMode graphics_mode(int row) {
+			if(
+				text_ ||
+				(mixed_ && row >= 160 && row < 192)
+			) return columns_80_ ? GraphicsMode::DoubleText : GraphicsMode::Text;
+			if(high_resolution_) {
+				return (annunciator_3_ && columns_80_) ? GraphicsMode::DoubleHighRes : GraphicsMode::HighRes;
+			} else {
+				if(columns_80_) return GraphicsMode::DoubleLowRes;
+				if(annunciator_3_) return GraphicsMode::FatLowRes;
+				return GraphicsMode::LowRes;
+			}
+		}
+
+		int video_page() {
+			return (store_80_ || !page2_) ? 0 : 1;
+		}
+
+		uint16_t get_row_address(int row) {
+			const int character_row = row >> 3;
+			const int pixel_row = row & 7;
+			const uint16_t row_address = static_cast<uint16_t>((character_row >> 3) * 40 + ((character_row&7) << 7));
+
+			const GraphicsMode pixel_mode = graphics_mode(row);
+			return ((pixel_mode == GraphicsMode::HighRes) || (pixel_mode == GraphicsMode::DoubleHighRes)) ?
+				static_cast<uint16_t>(((video_page()+1) * 0x2000) + row_address + ((pixel_row&7) << 10)) :
+				static_cast<uint16_t>(((video_page()+1) * 0x400) + row_address);
+		}
+
+		BusHandler &bus_handler_;
+};
+
+}
+}
+}
+
+#endif /* Video_hpp */

Machines/Apple/Macintosh/Audio.cpp

@@ -0,0 +1,97 @@
+//
+//  Audio.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 31/05/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#include "Audio.hpp"
+
+using namespace Apple::Macintosh;
+
+namespace {
+
+// The sample_length is coupled with the clock rate selected within the Macintosh proper;
+// as per the header-declaration a divide-by-two clock is expected to arrive here.
+const std::size_t sample_length = 352 / 2;
+
+}
+
+Audio::Audio(Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_(task_queue) {}
+
+// MARK: - Inputs
+
+void Audio::post_sample(uint8_t sample) {
+	// Store sample directly indexed by current write pointer; this ensures that collected samples
+	// directly map to volume and enabled/disabled states.
+	sample_queue_.buffer[sample_queue_.write_pointer] = sample;
+	sample_queue_.write_pointer = (sample_queue_.write_pointer + 1) % sample_queue_.buffer.size();
+}
+
+void Audio::set_volume(int volume) {
+	// Do nothing if the volume hasn't changed.
+	if(posted_volume_ == volume) return;
+	posted_volume_ = volume;
+
+	// Post the volume change as a deferred event.
+	task_queue_.defer([=] () {
+		volume_ = volume;
+		set_volume_multiplier();
+	});
+}
+
+void Audio::set_enabled(bool on) {
+	// Do nothing if the mask hasn't changed.
+	if(posted_enable_mask_ == int(on)) return;
+	posted_enable_mask_ = int(on);
+
+	// Post the enabled mask change as a deferred event.
+	task_queue_.defer([=] () {
+		enabled_mask_ = int(on);
+		set_volume_multiplier();
+	});
+}
+
+// MARK: - Output generation
+
+bool Audio::is_zero_level() {
+	return !volume_ || !enabled_mask_;
+}
+
+void Audio::set_sample_volume_range(std::int16_t range) {
+	// Some underflow here doesn't really matter.
+	output_volume_ = range / (7 * 255);
+	set_volume_multiplier();
+}
+
+void Audio::set_volume_multiplier() {
+	volume_multiplier_ = int16_t(output_volume_ * volume_ * enabled_mask_);
+}
+
+void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
+	// TODO: the implementation below acts as if the hardware uses pulse-amplitude modulation;
+	// in fact it uses pulse-width modulation. But the scale for pulses isn't specified, so
+	// that's something to return to.
+
+	while(number_of_samples) {
+		// Determine how many output samples will be at the same level.
+		const auto cycles_left_in_sample = std::min(number_of_samples, sample_length - subcycle_offset_);
+
+		// Determine the output level, and output that many samples.
+		// (Hoping that the copiler substitutes an effective memset16-type operation here).
+		const int16_t output_level = volume_multiplier_ * (int16_t(sample_queue_.buffer[sample_queue_.read_pointer]) - 128);
+		for(size_t c = 0; c < cycles_left_in_sample; ++c) {
+			target[c] = output_level;
+		}
+		target += cycles_left_in_sample;
+
+		// Advance the sample pointer.
+		subcycle_offset_ += cycles_left_in_sample;
+		sample_queue_.read_pointer = (sample_queue_.read_pointer + (subcycle_offset_ / sample_length)) % sample_queue_.buffer.size();
+		subcycle_offset_ %= sample_length;
+
+		// Decreate the number of samples left to write.
+		number_of_samples -= cycles_left_in_sample;
+	}
+}