Merge pull request #131 from TomHarte/ZX80FileFormats

Adds very preliminary emulation of the ZX80.
2024-12-26 09:29:45 +00:00 · 2017-06-15 18:32:38 -04:00 · 2017-06-15 18:32:38 -04:00 · 87496f9978
commit 87496f9978
parent 2190f60a89 d8e3103a2b
33 changed files with 1596 additions and 118 deletions
--- a/Machines/MemoryFuzzer.cpp
+++ b/Machines/MemoryFuzzer.cpp
@ -22,3 +22,7 @@ void Memory::Fuzz(uint8_t *buffer, size_t size) {
 		buffer[c] = (uint8_t)(std::rand() >> shift);
 	}
 }
+
+void Memory::Fuzz(std::vector<uint8_t> &buffer) {
+	Fuzz(buffer.data(), buffer.size());
+}
--- a/Machines/MemoryFuzzer.hpp
+++ b/Machines/MemoryFuzzer.hpp
@ -11,10 +11,12 @@

 #include <cstdint>
 #include <cstddef>
+#include <vector>

 namespace Memory {

 void Fuzz(uint8_t *buffer, size_t size);
+void Fuzz(std::vector<uint8_t> &buffer);

 }

--- a/Machines/ZX8081/Video.cpp
+++ b/Machines/ZX8081/Video.cpp
@ -0,0 +1,106 @@
+//
+//  Video.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 06/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#include "Video.hpp"
+
+using namespace ZX8081;
+
+Video::Video() :
+	crt_(new Outputs::CRT::CRT(207 * 2, 1, Outputs::CRT::DisplayType::PAL50, 1)),
+	line_data_(nullptr),
+	line_data_pointer_(nullptr),
+	cycles_since_update_(0),
+	sync_(false) {
+
+	// Set a composite sampling function that assumes 8bpp input grayscale.
+	// TODO: lessen this to 1bpp.
+	crt_->set_composite_sampling_function(
+		"float composite_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate, float phase, float amplitude)"
+		"{"
+			"return float(texture(texID, coordinate).r) / 255.0;"
+		"}");
+
+	// Show only the centre 80% of the TV frame.
+	crt_->set_visible_area(Outputs::CRT::Rect(0.1f, 0.1f, 0.8f, 0.8f));
+}
+
+void Video::run_for_cycles(int number_of_cycles) {
+	// Just keep a running total of the amount of time that remains owed to the CRT.
+	cycles_since_update_ += (unsigned int)number_of_cycles << 1;
+}
+
+void Video::flush() {
+	flush(sync_);
+}
+
+void Video::flush(bool next_sync) {
+	if(sync_) {
+		// If in sync, that takes priority. Output the proper amount of sync.
+		crt_->output_sync(cycles_since_update_);
+	} else {
+		// If not presently in sync, then...
+
+		if(line_data_) {
+			// If there is output data queued, output it either if it's being interrupted by
+			// sync, or if we're past its end anyway. Otherwise let it be.
+			unsigned int data_length = (unsigned int)(line_data_pointer_ - line_data_);
+			if(data_length < cycles_since_update_ || next_sync) {
+				crt_->output_data(data_length, 1);
+				line_data_pointer_ = line_data_ = nullptr;
+				cycles_since_update_ -= data_length;
+			} else return;
+		}
+
+		// Any pending pixels being dealt with, pad with the white level.
+		uint8_t *colour_pointer = (uint8_t *)crt_->allocate_write_area(1);
+		if(colour_pointer) *colour_pointer = 0xff;
+		crt_->output_level(cycles_since_update_);
+	}
+
+	cycles_since_update_ = 0;
+}
+
+void Video::set_sync(bool sync) {
+	// Do nothing if sync hasn't changed.
+	if(sync_ == sync) return;
+
+	// Complete whatever was being drawn, and update sync.
+	flush(sync);
+	sync_ = sync;
+}
+
+void Video::output_byte(uint8_t byte) {
+	// Complete whatever was going on.
+	flush();
+
+	// Grab a buffer if one isn't already available.
+	if(!line_data_) {
+		line_data_pointer_ = line_data_ = crt_->allocate_write_area(320);
+	}
+
+	// If a buffer was obtained, serialise the new pixels.
+	if(line_data_) {
+		uint8_t mask = 0x80;
+		for(int c = 0; c < 8; c++) {
+			line_data_pointer_[c] = (byte & mask) ? 0xff : 0x00;
+			mask >>= 1;
+		}
+		line_data_pointer_ += 8;
+
+		// If that fills the buffer, output it now.
+		if(line_data_pointer_ - line_data_ == 320) {
+			crt_->output_data(320, 1);
+			line_data_pointer_ = line_data_ = nullptr;
+			cycles_since_update_ -= 160;
+		}
+	}
+}
+
+std::shared_ptr<Outputs::CRT::CRT> Video::get_crt() {
+	return crt_;
+}
--- a/Machines/ZX8081/Video.hpp
+++ b/Machines/ZX8081/Video.hpp
@ -0,0 +1,54 @@
+//
+//  Video.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 06/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#ifndef Machines_ZX8081_Video_hpp
+#define Machines_ZX8081_Video_hpp
+
+#include "../../Outputs/CRT/CRT.hpp"
+
+namespace ZX8081 {
+
+/*!
+	Packages a ZX80/81-style video feed into a CRT-compatible waveform.
+
+	While sync is active, this feed will output the sync level.
+
+	While sync is inactive, this feed will output the white level unless it is supplied
+	with a byte to output. When a byte is supplied for output, it will be interpreted as
+	a 1-bit graphic and output over the next 4 cycles, picking between the white level
+	and the black level.
+*/
+class Video {
+	public:
+		/// Constructs an instance of the video feed; a CRT is also created.
+		Video();
+		/// @returns The CRT this video feed is feeding.
+		std::shared_ptr<Outputs::CRT::CRT> get_crt();
+
+		/// Advances time by @c number_of_cycles cycles.
+		void run_for_cycles(int number_of_cycles);
+		/// Forces output to catch up to the current output position.
+		void flush();
+
+		/// Sets the current sync output.
+		void set_sync(bool sync);
+		/// Causes @c byte to be serialised into pixels and output over the next four cycles.
+		void output_byte(uint8_t byte);
+
+	private:
+		bool sync_;
+		uint8_t *line_data_, *line_data_pointer_;
+		unsigned int cycles_since_update_;
+		std::shared_ptr<Outputs::CRT::CRT> crt_;
+
+		void flush(bool next_sync);
+};
+
+}
+
+#endif /* Video_hpp */
--- a/Machines/ZX8081/ZX8081.cpp
+++ b/Machines/ZX8081/ZX8081.cpp
@ -0,0 +1,252 @@
+//
+//  ZX8081.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 04/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#include "ZX8081.hpp"
+
+#include "../MemoryFuzzer.hpp"
+
+using namespace ZX8081;
+
+namespace {
+	// The clock rate is 3.25Mhz.
+	const unsigned int ZX8081ClockRate = 3250000;
+}
+
+Machine::Machine() :
+	vsync_(false),
+	hsync_(false),
+	nmi_is_enabled_(false),
+	tape_player_(ZX8081ClockRate) {
+	set_clock_rate(ZX8081ClockRate);
+	tape_player_.set_motor_control(true);
+	clear_all_keys();
+}
+
+int Machine::perform_machine_cycle(const CPU::Z80::MachineCycle &cycle) {
+	int wait_cycles = 0;
+
+	int previous_counter = horizontal_counter_;
+	horizontal_counter_ += cycle.length;
+
+	if(previous_counter < vsync_start_cycle_ && horizontal_counter_ >= vsync_start_cycle_) {
+		video_->run_for_cycles(vsync_start_cycle_ - previous_counter);
+		set_hsync(true);
+		if(nmi_is_enabled_) {
+			set_non_maskable_interrupt_line(true);
+			if(!get_halt_line()) {
+				wait_cycles = vsync_end_cycle_ - horizontal_counter_;
+			}
+		}
+		video_->run_for_cycles(horizontal_counter_ - vsync_start_cycle_ + wait_cycles);
+	} else if(previous_counter <= vsync_end_cycle_ && horizontal_counter_ > vsync_end_cycle_) {
+		video_->run_for_cycles(vsync_end_cycle_ - previous_counter);
+		set_hsync(false);
+		if(nmi_is_enabled_) set_non_maskable_interrupt_line(false);
+		video_->run_for_cycles(horizontal_counter_ - vsync_end_cycle_);
+	} else {
+		video_->run_for_cycles(cycle.length);
+	}
+
+	horizontal_counter_ += wait_cycles;
+	if(is_zx81_) horizontal_counter_ %= 207;
+
+//	tape_player_.run_for_cycles(cycle.length + wait_cycles);
+
+	uint16_t refresh = 0;
+	uint16_t address = cycle.address ? *cycle.address : 0;
+	switch(cycle.operation) {
+		case CPU::Z80::BusOperation::Output:
+			set_vsync(false);
+			line_counter_ = 0;
+
+			switch(address & 7) {
+				default: break;
+				case 0x5:	nmi_is_enabled_ = false;		break;
+				case 0x6:	nmi_is_enabled_ = is_zx81_;		break;
+			}
+		break;
+
+		case CPU::Z80::BusOperation::Input: {
+			uint8_t value = 0xff;
+			if(!(address&1)) {
+				set_vsync(true);
+
+				uint16_t mask = 0x100;
+				for(int c = 0; c < 8; c++) {
+					if(!(address & mask)) value &= key_states_[c];
+					mask <<= 1;
+				}
+
+				value &= ~(tape_player_.get_input() ? 0x00 : 0x80);
+			}
+			*cycle.value = value;
+		} break;
+
+		case CPU::Z80::BusOperation::Interrupt:
+			line_counter_ = (line_counter_ + 1) & 7;
+			*cycle.value = 0xff;
+			horizontal_counter_ = 0;
+		break;
+
+		case CPU::Z80::BusOperation::ReadOpcode:
+			// The ZX80 and 81 signal an interrupt while refresh is active and bit 6 of the refresh
+			// address is low. The Z80 signals a refresh, providing the refresh address during the
+			// final two cycles of an opcode fetch. Therefore communicate a transient signalling
+			// of the IRQ line if necessary.
+			refresh = get_value_of_register(CPU::Z80::Register::Refresh);
+			set_interrupt_line(!(refresh & 0x40), -2);
+			set_interrupt_line(false);
+
+			// Check for use of the fast tape hack.
+			if(address == tape_trap_address_) { // TODO: && fast_tape_hack_enabled_
+				int next_byte = parser_.get_next_byte(tape_player_.get_tape());
+				if(next_byte != -1) {
+					uint16_t hl = get_value_of_register(CPU::Z80::Register::HL);
+					ram_[hl & ram_mask_] = (uint8_t)next_byte;
+					*cycle.value = 0x00;
+					set_value_of_register(CPU::Z80::Register::ProgramCounter, tape_return_address_ - 1);
+					return 0;
+				}
+			}
+
+		case CPU::Z80::BusOperation::Read:
+			if(address < ram_base_) {
+				*cycle.value = rom_[address & rom_mask_];
+			} else {
+				uint8_t value = ram_[address & ram_mask_];
+
+				// If this is an M1 cycle reading from above the 32kb mark and HALT is not
+				// currently active, perform a video output and return a NOP. Otherwise,
+				// just return the value as read.
+				if(cycle.operation == CPU::Z80::BusOperation::ReadOpcode && address&0x8000 && !(value & 0x40) && !get_halt_line()) {
+					size_t char_address = (size_t)((refresh & 0xff00) | ((value & 0x3f) << 3) | line_counter_);
+					if(char_address < ram_base_) {
+						uint8_t mask = (value & 0x80) ? 0x00 : 0xff;
+						value = rom_[char_address & rom_mask_] ^ mask;
+					}
+
+					video_->output_byte(value);
+					*cycle.value = 0;
+				} else *cycle.value = value;
+			}
+		break;
+
+		case CPU::Z80::BusOperation::Write:
+			if(address >= ram_base_) {
+				ram_[address & ram_mask_] = *cycle.value;
+			}
+		break;
+
+		default: break;
+	}
+
+	return wait_cycles;
+}
+
+void Machine::flush() {
+	video_->flush();
+}
+
+void Machine::setup_output(float aspect_ratio) {
+	video_.reset(new Video);
+}
+
+void Machine::close_output() {
+	video_.reset();
+}
+
+std::shared_ptr<Outputs::CRT::CRT> Machine::get_crt() {
+	return video_->get_crt();
+}
+
+std::shared_ptr<Outputs::Speaker> Machine::get_speaker() {
+	return nullptr;
+}
+
+void Machine::run_for_cycles(int number_of_cycles) {
+	CPU::Z80::Processor<Machine>::run_for_cycles(number_of_cycles);
+}
+
+void Machine::configure_as_target(const StaticAnalyser::Target &target) {
+	is_zx81_ = target.zx8081.isZX81;
+	if(is_zx81_) {
+		rom_ = zx81_rom_;
+		tape_trap_address_ = 0x37c;
+		tape_return_address_ = 0x380;
+		vsync_start_cycle_ = 13;
+		vsync_end_cycle_ = 33;
+		vsync_start_cycle_ = 16;
+		vsync_end_cycle_ = 32;
+	} else {
+		rom_ = zx80_rom_;
+		tape_trap_address_ = 0x220;
+		tape_return_address_ = 0x248;
+		vsync_start_cycle_ = 13;
+		vsync_end_cycle_ = 33;
+	}
+	rom_mask_ = (uint16_t)(rom_.size() - 1);
+
+	switch(target.zx8081.memory_model) {
+		case StaticAnalyser::ZX8081MemoryModel::Unexpanded:
+			ram_.resize(1024);
+			ram_base_ = 16384;
+			ram_mask_ = 1023;
+		break;
+		case StaticAnalyser::ZX8081MemoryModel::SixteenKB:
+			ram_.resize(16384);
+			ram_base_ = 16384;
+			ram_mask_ = 16383;
+		break;
+		case StaticAnalyser::ZX8081MemoryModel::SixtyFourKB:
+			ram_.resize(65536);
+			ram_base_ = 8192;
+			ram_mask_ = 65535;
+		break;
+	}
+	Memory::Fuzz(ram_);
+
+	if(target.tapes.size()) {
+		tape_player_.set_tape(target.tapes.front());
+	}
+}
+
+void Machine::set_rom(ROMType type, std::vector<uint8_t> data) {
+	switch(type) {
+		case ZX80: zx80_rom_ = data; break;
+		case ZX81: zx81_rom_ = data; break;
+	}
+}
+
+#pragma mark - Video
+
+void Machine::set_vsync(bool sync) {
+	vsync_ = sync;
+	update_sync();
+}
+
+void Machine::set_hsync(bool sync) {
+	hsync_ = sync;
+	update_sync();
+}
+
+void Machine::update_sync() {
+	video_->set_sync(vsync_ || hsync_);
+}
+
+#pragma mark - Keyboard
+
+void Machine::set_key_state(uint16_t key, bool isPressed) {
+	if(isPressed)
+		key_states_[key >> 8] &= (uint8_t)(~key);
+	else
+		key_states_[key >> 8] |= (uint8_t)key;
+}
+
+void Machine::clear_all_keys() {
+	memset(key_states_, 0xff, 8);
+}
--- a/Machines/ZX8081/ZX8081.hpp
+++ b/Machines/ZX8081/ZX8081.hpp
@ -0,0 +1,96 @@
+//
+//  ZX8081.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 04/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#ifndef ZX8081_hpp
+#define ZX8081_hpp
+
+#include "../ConfigurationTarget.hpp"
+#include "../CRTMachine.hpp"
+
+#include "../../Processors/Z80/Z80.hpp"
+#include "../../Storage/Tape/Tape.hpp"
+#include "../../Storage/Tape/Parsers/ZX8081.hpp"
+
+#include "Video.hpp"
+
+#include <cstdint>
+#include <vector>
+
+namespace ZX8081 {
+
+enum ROMType: uint8_t {
+	ZX80, ZX81
+};
+
+enum Key: uint16_t {
+	KeyShift	= 0x0000 | 0x01,	KeyZ	= 0x0000 | 0x02,	KeyX = 0x0000 | 0x04,	KeyC = 0x0000 | 0x08,	KeyV = 0x0000 | 0x10,
+	KeyA		= 0x0100 | 0x01,	KeyS	= 0x0100 | 0x02,	KeyD = 0x0100 | 0x04,	KeyF = 0x0100 | 0x08,	KeyG = 0x0100 | 0x10,
+	KeyQ		= 0x0200 | 0x01,	KeyW	= 0x0200 | 0x02,	KeyE = 0x0200 | 0x04,	KeyR = 0x0200 | 0x08,	KeyT = 0x0200 | 0x10,
+	Key1		= 0x0300 | 0x01,	Key2	= 0x0300 | 0x02,	Key3 = 0x0300 | 0x04,	Key4 = 0x0300 | 0x08,	Key5 = 0x0300 | 0x10,
+	Key0		= 0x0400 | 0x01,	Key9	= 0x0400 | 0x02,	Key8 = 0x0400 | 0x04,	Key7 = 0x0400 | 0x08,	Key6 = 0x0400 | 0x10,
+	KeyP		= 0x0500 | 0x01,	KeyO	= 0x0500 | 0x02,	KeyI = 0x0500 | 0x04,	KeyU = 0x0500 | 0x08,	KeyY = 0x0500 | 0x10,
+	KeyEnter	= 0x0600 | 0x01,	KeyL	= 0x0600 | 0x02,	KeyK = 0x0600 | 0x04,	KeyJ = 0x0600 | 0x08,	KeyH = 0x0600 | 0x10,
+	KeySpace	= 0x0700 | 0x01,	KeyDot	= 0x0700 | 0x02,	KeyM = 0x0700 | 0x04,	KeyN = 0x0700 | 0x08,	KeyB = 0x0700 | 0x10,
+};
+
+class Machine:
+	public CPU::Z80::Processor<Machine>,
+	public CRTMachine::Machine,
+	public ConfigurationTarget::Machine {
+	public:
+		Machine();
+
+		int perform_machine_cycle(const CPU::Z80::MachineCycle &cycle);
+		void flush();
+
+		void setup_output(float aspect_ratio);
+		void close_output();
+
+		std::shared_ptr<Outputs::CRT::CRT> get_crt();
+		std::shared_ptr<Outputs::Speaker> get_speaker();
+
+		void run_for_cycles(int number_of_cycles);
+
+		void configure_as_target(const StaticAnalyser::Target &target);
+
+		void set_rom(ROMType type, std::vector<uint8_t> data);
+		void set_key_state(uint16_t key, bool isPressed);
+		void clear_all_keys();
+
+	private:
+		std::shared_ptr<Video> video_;
+		std::vector<uint8_t> zx81_rom_, zx80_rom_;
+		uint16_t tape_trap_address_, tape_return_address_;
+
+		std::vector<uint8_t> ram_;
+		uint16_t ram_mask_, ram_base_;
+
+		std::vector<uint8_t> rom_;
+		uint16_t rom_mask_;
+
+		bool vsync_, hsync_;
+		int line_counter_;
+
+		uint8_t key_states_[8];
+
+		void set_vsync(bool sync);
+		void set_hsync(bool sync);
+		void update_sync();
+
+		Storage::Tape::BinaryTapePlayer tape_player_;
+		Storage::Tape::ZX8081::Parser parser_;
+
+		int horizontal_counter_;
+		bool is_zx81_;
+		bool nmi_is_enabled_;
+		int vsync_start_cycle_, vsync_end_cycle_;
+};
+
+}
+
+#endif /* ZX8081_hpp */
--- a/Signal.xcodeproj/project.pbxproj
+++ b/Signal.xcodeproj/project.pbxproj
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@ -379,6 +385,7 @@
 		4BBF99141C8FBA6F0075DAFB /* TextureBuilder.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BBF99081C8FBA6F0075DAFB /* TextureBuilder.cpp */; };
 		4BBF99151C8FBA6F0075DAFB /* CRTOpenGL.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BBF990A1C8FBA6F0075DAFB /* CRTOpenGL.cpp */; };
 		4BBF99181C8FBA6F0075DAFB /* TextureTarget.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BBF99121C8FBA6F0075DAFB /* TextureTarget.cpp */; };
+		4BBFBB6C1EE8401E00C01E7A /* ZX8081.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BBFBB6A1EE8401E00C01E7A /* ZX8081.cpp */; };
 		4BC3B74F1CD194CC00F86E85 /* Shader.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC3B74D1CD194CC00F86E85 /* Shader.cpp */; };
 		4BC3B7521CD1956900F86E85 /* OutputShader.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC3B7501CD1956900F86E85 /* OutputShader.cpp */; };
 		4BC5E4921D7ED365008CF980 /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC5E4901D7ED365008CF980 /* StaticAnalyser.cpp */; };
@ -398,6 +405,7 @@
 		4BCF1FA81DADC5250039D2E7 /* CSOric.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4BCF1FA71DADC5250039D2E7 /* CSOric.mm */; };
 		4BCF1FAB1DADD41B0039D2E7 /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BCF1FA91DADD41B0039D2E7 /* StaticAnalyser.cpp */; };
 		4BD14B111D74627C0088EAD6 /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BD14B0F1D74627C0088EAD6 /* StaticAnalyser.cpp */; };
+		4BD3A30B1EE755C800B5B501 /* Video.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BD3A3091EE755C800B5B501 /* Video.cpp */; };
 		4BD468F71D8DF41D0084958B /* 1770.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BD468F51D8DF41D0084958B /* 1770.cpp */; };
 		4BD4A8CD1E077E8A0020D856 /* PCMSegment.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B121F961E060CF000BFDA12 /* PCMSegment.cpp */; };
 		4BD4A8D01E077FD20020D856 /* PCMTrackTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4BD4A8CF1E077FD20020D856 /* PCMTrackTests.mm */; };
@ -464,6 +472,15 @@
 		4B14145A1B58879D00E04248 /* 6502AllRAM.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = 6502AllRAM.hpp; sourceTree = "<group>"; };
 		4B14145F1B58885000E04248 /* WolfgangLorenzTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = WolfgangLorenzTests.swift; sourceTree = "<group>"; };
 		4B1414611B58888700E04248 /* KlausDormannTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = KlausDormannTests.swift; sourceTree = "<group>"; };
+		4B1497861EE4A1DA00CE2596 /* ZX80O81P.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = ZX80O81P.cpp; sourceTree = "<group>"; };
+		4B1497871EE4A1DA00CE2596 /* ZX80O81P.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = ZX80O81P.hpp; sourceTree = "<group>"; };
+		4B1497891EE4AC5E00CE2596 /* StaticAnalyser.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = StaticAnalyser.cpp; path = ../../StaticAnalyser/ZX8081/StaticAnalyser.cpp; sourceTree = "<group>"; };
+		4B14978A1EE4AC5E00CE2596 /* StaticAnalyser.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = StaticAnalyser.hpp; path = ../../StaticAnalyser/ZX8081/StaticAnalyser.hpp; sourceTree = "<group>"; };
+		4B14978D1EE4B4D200CE2596 /* CSZX8081.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = CSZX8081.h; sourceTree = "<group>"; };
+		4B14978E1EE4B4D200CE2596 /* CSZX8081.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = CSZX8081.mm; sourceTree = "<group>"; };
+		4B1497901EE4B5A800CE2596 /* ZX8081.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = ZX8081.cpp; path = ZX8081/ZX8081.cpp; sourceTree = "<group>"; };
+		4B1497911EE4B5A800CE2596 /* ZX8081.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = ZX8081.hpp; path = ZX8081/ZX8081.hpp; sourceTree = "<group>"; };
+		4B1497971EE4B97F00CE2596 /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = "Clock Signal/Base.lproj/ZX8081Options.xib"; sourceTree = SOURCE_ROOT; };
 		4B1D08051E0F7A1100763741 /* TimeTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = TimeTests.mm; sourceTree = "<group>"; };
 		4B1E85731D170228001EF87D /* Typer.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = Typer.cpp; sourceTree = "<group>"; };
 		4B1E85741D170228001EF87D /* Typer.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Typer.hpp; sourceTree = "<group>"; };
@ -595,6 +612,8 @@
 		4B96F7211D75119A0058BB2D /* Tape.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = Tape.hpp; path = ../../StaticAnalyser/Acorn/Tape.hpp; sourceTree = "<group>"; };
 		4B9CCDA01DA279CA0098B625 /* Vic20OptionsPanel.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Vic20OptionsPanel.swift; sourceTree = "<group>"; };
 		4B9CCDA21DA27C3F0098B625 /* CSJoystickMachine.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = CSJoystickMachine.h; sourceTree = "<group>"; };
+		4BA0F68C1EEA0E8400E9489E /* ZX8081.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = ZX8081.cpp; path = Data/ZX8081.cpp; sourceTree = "<group>"; };
+		4BA0F68D1EEA0E8400E9489E /* ZX8081.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = ZX8081.hpp; path = Data/ZX8081.hpp; sourceTree = "<group>"; };
 		4BA22B051D8817CE0008C640 /* Disk.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = Disk.cpp; path = ../../StaticAnalyser/Commodore/Disk.cpp; sourceTree = "<group>"; };
 		4BA22B061D8817CE0008C640 /* Disk.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = Disk.hpp; path = ../../StaticAnalyser/Commodore/Disk.hpp; sourceTree = "<group>"; };
 		4BA61EAE1D91515900B3C876 /* NSData+StdVector.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSData+StdVector.h"; sourceTree = "<group>"; };
@ -907,6 +926,8 @@
 		4BBF99121C8FBA6F0075DAFB /* TextureTarget.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = TextureTarget.cpp; sourceTree = "<group>"; };
 		4BBF99131C8FBA6F0075DAFB /* TextureTarget.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = TextureTarget.hpp; sourceTree = "<group>"; };
 		4BBF99191C8FC2750075DAFB /* CRTTypes.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = CRTTypes.hpp; sourceTree = "<group>"; };
+		4BBFBB6A1EE8401E00C01E7A /* ZX8081.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = ZX8081.cpp; path = Parsers/ZX8081.cpp; sourceTree = "<group>"; };
+		4BBFBB6B1EE8401E00C01E7A /* ZX8081.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = ZX8081.hpp; path = Parsers/ZX8081.hpp; sourceTree = "<group>"; };
 		4BC3B74D1CD194CC00F86E85 /* Shader.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = Shader.cpp; sourceTree = "<group>"; };
 		4BC3B74E1CD194CC00F86E85 /* Shader.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Shader.hpp; sourceTree = "<group>"; };
 		4BC3B7501CD1956900F86E85 /* OutputShader.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = OutputShader.cpp; sourceTree = "<group>"; };
@ -939,6 +960,8 @@
 		4BCF1FAA1DADD41B0039D2E7 /* StaticAnalyser.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = StaticAnalyser.hpp; path = ../../StaticAnalyser/Oric/StaticAnalyser.hpp; sourceTree = "<group>"; };
 		4BD14B0F1D74627C0088EAD6 /* StaticAnalyser.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = StaticAnalyser.cpp; path = ../../StaticAnalyser/Acorn/StaticAnalyser.cpp; sourceTree = "<group>"; };
 		4BD14B101D74627C0088EAD6 /* StaticAnalyser.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = StaticAnalyser.hpp; path = ../../StaticAnalyser/Acorn/StaticAnalyser.hpp; sourceTree = "<group>"; };
+		4BD3A3091EE755C800B5B501 /* Video.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = Video.cpp; path = ZX8081/Video.cpp; sourceTree = "<group>"; };
+		4BD3A30A1EE755C800B5B501 /* Video.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = Video.hpp; path = ZX8081/Video.hpp; sourceTree = "<group>"; };
 		4BD468F51D8DF41D0084958B /* 1770.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = 1770.cpp; path = 1770/1770.cpp; sourceTree = "<group>"; };
 		4BD468F61D8DF41D0084958B /* 1770.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = 1770.hpp; path = 1770/1770.hpp; sourceTree = "<group>"; };
 		4BD4A8CF1E077FD20020D856 /* PCMTrackTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = PCMTrackTests.mm; sourceTree = "<group>"; };
@ -1064,6 +1087,26 @@
 			name = "Test Binaries";
 			sourceTree = "<group>";
 		};
+		4B14978C1EE4AC6200CE2596 /* ZX80/81 */ = {
+			isa = PBXGroup;
+			children = (
+				4B1497891EE4AC5E00CE2596 /* StaticAnalyser.cpp */,
+				4B14978A1EE4AC5E00CE2596 /* StaticAnalyser.hpp */,
+			);
+			name = ZX80/81;
+			sourceTree = "<group>";
+		};
+		4B1497931EE4B5AC00CE2596 /* ZX8081 */ = {
+			isa = PBXGroup;
+			children = (
+				4B1497901EE4B5A800CE2596 /* ZX8081.cpp */,
+				4B1497911EE4B5A800CE2596 /* ZX8081.hpp */,
+				4BD3A3091EE755C800B5B501 /* Video.cpp */,
+				4BD3A30A1EE755C800B5B501 /* Video.hpp */,
+			);
+			name = ZX8081;
+			sourceTree = "<group>";
+		};
 		4B1E85791D174DEC001EF87D /* 6532 */ = {
 			isa = PBXGroup;
 			children = (
@ -1129,13 +1172,15 @@
 			isa = PBXGroup;
 			children = (
 				4B2A53991D117D36003C6002 /* CSAtari2600.h */,
-				4B2A539A1D117D36003C6002 /* CSAtari2600.mm */,
 				4B2A539B1D117D36003C6002 /* CSElectron.h */,
-				4B2A539C1D117D36003C6002 /* CSElectron.mm */,
 				4BCF1FA61DADC5250039D2E7 /* CSOric.h */,
-				4BCF1FA71DADC5250039D2E7 /* CSOric.mm */,
 				4B2A539D1D117D36003C6002 /* CSVic20.h */,
+				4B14978D1EE4B4D200CE2596 /* CSZX8081.h */,
+				4B2A539A1D117D36003C6002 /* CSAtari2600.mm */,
+				4B2A539C1D117D36003C6002 /* CSElectron.mm */,
+				4BCF1FA71DADC5250039D2E7 /* CSOric.mm */,
 				4B2A539E1D117D36003C6002 /* CSVic20.mm */,
+				4B14978E1EE4B4D200CE2596 /* CSZX8081.mm */,
 			);
 			path = Wrappers;
 			sourceTree = "<group>";
@ -1270,6 +1315,7 @@
 				4B8FE2151DA19D5F0090D3CE /* MachineDocument.xib */,
 				4B2A332B1DB86821002876E3 /* OricOptions.xib */,
 				4B8FE2191DA19D5F0090D3CE /* Vic20Options.xib */,
+				4B1497961EE4B97F00CE2596 /* ZX8081Options.xib */,
 			);
 			path = Documents;
 			sourceTree = "<group>";
@ -1312,15 +1358,15 @@
 		4B69FB391C4D908A00B5F0AA /* Storage */ = {
 			isa = PBXGroup;
 			children = (
+				4B5FADB81DE3151600AEC565 /* FileHolder.cpp */,
 				4BB697C91D4B6D3E00248BDF /* TimedEventLoop.cpp */,
+				4B5FADB91DE3151600AEC565 /* FileHolder.hpp */,
 				4BAB62AE1D32730D00DF5BA0 /* Storage.hpp */,
 				4BB697CA1D4B6D3E00248BDF /* TimedEventLoop.hpp */,
 				4BEE0A691D72496600532C7B /* Cartridge */,
 				4B8805F81DCFF6CD003085B1 /* Data */,
 				4BAB62AA1D3272D200DF5BA0 /* Disk */,
 				4B69FB3A1C4D908A00B5F0AA /* Tape */,
-				4B5FADB81DE3151600AEC565 /* FileHolder.cpp */,
-				4B5FADB91DE3151600AEC565 /* FileHolder.hpp */,
 			);
 			name = Storage;
 			path = ../../Storage;
@ -1349,6 +1395,8 @@
 				4B2BFC5E1D613E0200BA3AA9 /* TapePRG.hpp */,
 				4B59199A1DAC6C46005BB85C /* OricTAP.cpp */,
 				4B59199B1DAC6C46005BB85C /* OricTAP.hpp */,
+				4B1497861EE4A1DA00CE2596 /* ZX80O81P.cpp */,
+				4B1497871EE4A1DA00CE2596 /* ZX80O81P.hpp */,
 			);
 			path = Formats;
 			sourceTree = "<group>";
@ -1373,6 +1421,8 @@
 				4B8805F31DCFD22A003085B1 /* Commodore.hpp */,
 				4B8805F91DCFF807003085B1 /* Oric.cpp */,
 				4B8805FA1DCFF807003085B1 /* Oric.hpp */,
+				4BBFBB6A1EE8401E00C01E7A /* ZX8081.cpp */,
+				4BBFBB6B1EE8401E00C01E7A /* ZX8081.hpp */,
 			);
 			name = Parsers;
 			sourceTree = "<group>";
@ -1381,7 +1431,9 @@
 			isa = PBXGroup;
 			children = (
 				4B8805F51DCFF6C9003085B1 /* Commodore.cpp */,
+				4BA0F68C1EEA0E8400E9489E /* ZX8081.cpp */,
 				4B8805F61DCFF6C9003085B1 /* Commodore.hpp */,
+				4BA0F68D1EEA0E8400E9489E /* ZX8081.hpp */,
 			);
 			name = Data;
 			sourceTree = "<group>";
@ -1834,6 +1886,7 @@
 				4B4DC81D1D2C2425003C5BF8 /* Commodore */,
 				4B2E2D9E1C3A070900138695 /* Electron */,
 				4BCF1FA51DADC3E10039D2E7 /* Oric */,
+				4B1497931EE4B5AC00CE2596 /* ZX8081 */,
 			);
 			name = Machines;
 			path = ../../Machines;
@ -2072,8 +2125,9 @@
 				4BD14B121D7462810088EAD6 /* Acorn */,
 				4BA799961D8B65730045123D /* Atari */,
 				4BC830D21D6E7C6D0000A26F /* Commodore */,
-				4BCF1FAC1DADD41F0039D2E7 /* Oric */,
 				4B5A12581DD55873007A2231 /* Disassembler */,
+				4BCF1FAC1DADD41F0039D2E7 /* Oric */,
+				4B14978C1EE4AC6200CE2596 /* ZX80/81 */,
 			);
 			name = StaticAnalyser;
 			sourceTree = "<group>";
@ -2203,6 +2257,7 @@
 				4B8FE21D1DA19D5F0090D3CE /* ElectronOptions.xib in Resources */,
 				4B79E4461E3AF38600141F11 /* floppy525.png in Resources */,
 				4BC9DF451D044FCA00F44158 /* ROMImages in Resources */,
+				4B1497981EE4B97F00CE2596 /* ZX8081Options.xib in Resources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@ -2512,6 +2567,7 @@
 				4BCF1FA41DADC3DD0039D2E7 /* Oric.cpp in Sources */,
 				4BEA525E1DF33323007E74F2 /* Tape.cpp in Sources */,
 				4BC8A62D1DCE60E000DAC693 /* Typer.cpp in Sources */,
+				4B1497921EE4B5A800CE2596 /* ZX8081.cpp in Sources */,
 				4B643F3F1D77B88000D431D6 /* DocumentController.swift in Sources */,
 				4BA799951D8B656E0045123D /* StaticAnalyser.cpp in Sources */,
 				4B2BFDB21DAEF5FF001A68B8 /* Video.cpp in Sources */,
@ -2542,14 +2598,18 @@
 				4BF8295D1D8F048B001BAE39 /* MFM.cpp in Sources */,
 				4BE77A2E1D84ADFB00BC3827 /* File.cpp in Sources */,
 				4B5FADBD1DE31D1500AEC565 /* OricMFMDSK.cpp in Sources */,
+				4B14978B1EE4AC5E00CE2596 /* StaticAnalyser.cpp in Sources */,
+				4BA0F68E1EEA0E8400E9489E /* ZX8081.cpp in Sources */,
 				4B77069D1EC904570053B588 /* Z80.cpp in Sources */,
 				4BAB62B51D327F7E00DF5BA0 /* G64.cpp in Sources */,
 				4BD468F71D8DF41D0084958B /* 1770.cpp in Sources */,
+				4BD3A30B1EE755C800B5B501 /* Video.cpp in Sources */,
 				4BBF99141C8FBA6F0075DAFB /* TextureBuilder.cpp in Sources */,
 				4BCF1FA81DADC5250039D2E7 /* CSOric.mm in Sources */,
 				4B5FADBA1DE3151600AEC565 /* FileHolder.cpp in Sources */,
 				4B6C73BD1D387AE500AFCFCA /* DiskController.cpp in Sources */,
 				4B643F3A1D77AD1900D431D6 /* CSStaticAnalyser.mm in Sources */,
+				4B1497881EE4A1DA00CE2596 /* ZX80O81P.cpp in Sources */,
 				4B4DC8281D2C2470003C5BF8 /* C1540.cpp in Sources */,
 				4B5A12571DD55862007A2231 /* Disassembler6502.cpp in Sources */,
 				4BE7C9181E3D397100A5496D /* TIA.cpp in Sources */,
@ -2578,6 +2638,7 @@
 				4BCA6CC81D9DD9F000C2D7B2 /* CommodoreROM.cpp in Sources */,
 				4BA22B071D8817CE0008C640 /* Disk.cpp in Sources */,
 				4BEA52661DF3472B007E74F2 /* Speaker.cpp in Sources */,
+				4BBFBB6C1EE8401E00C01E7A /* ZX8081.cpp in Sources */,
 				4BC3B7521CD1956900F86E85 /* OutputShader.cpp in Sources */,
 				4B4C83701D4F623200CD541F /* D64.cpp in Sources */,
 				4B5073071DDD3B9400C48FBD /* ArrayBuilder.cpp in Sources */,
@ -2588,6 +2649,7 @@
 				4BEE0A701D72496600532C7B /* PRG.cpp in Sources */,
 				4B8FE2271DA1DE2D0090D3CE /* NSBundle+DataResource.m in Sources */,
 				4B2A53A01D117D36003C6002 /* CSMachine.mm in Sources */,
+				4B14978F1EE4B4D200CE2596 /* CSZX8081.mm in Sources */,
 				4BC91B831D1F160E00884B76 /* CommodoreTAP.cpp in Sources */,
 				4BCF1FAB1DADD41B0039D2E7 /* StaticAnalyser.cpp in Sources */,
 				4B2A539F1D117D36003C6002 /* CSAudioQueue.m in Sources */,
@ -2660,6 +2722,14 @@
 /* End PBXTargetDependency section */

 /* Begin PBXVariantGroup section */
+		4B1497961EE4B97F00CE2596 /* ZX8081Options.xib */ = {
+			isa = PBXVariantGroup;
+			children = (
+				4B1497971EE4B97F00CE2596 /* Base */,
+			);
+			name = ZX8081Options.xib;
+			sourceTree = "<group>";
+		};
 		4B2A332B1DB86821002876E3 /* OricOptions.xib */ = {
 			isa = PBXVariantGroup;
 			children = (
--- a/Signal.xcodeproj/xcshareddata/xcschemes/Clock
+++ b/Signal.xcodeproj/xcshareddata/xcschemes/Clock
@ -68,7 +68,7 @@
      </AdditionalOptions>
   </TestAction>
   <LaunchAction
-      buildConfiguration = "Release"
+      buildConfiguration = "Debug"
      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
      launchStyle = "0"
--- a/Signal/Base.lproj/ZX8081Options.xib
+++ b/Signal/Base.lproj/ZX8081Options.xib
@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="12120" systemVersion="16F73" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
+    <dependencies>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="12120"/>
+        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
+    </dependencies>
+    <objects>
+        <customObject id="-2" userLabel="File's Owner" customClass="MachineDocument" customModule="Clock_Signal" customModuleProvider="target">
+            <connections>
+                <outlet property="optionsPanel" destination="ota-g7-hOL" id="zeO-di-9i3"/>
+            </connections>
+        </customObject>
+        <customObject id="-1" userLabel="First Responder" customClass="FirstResponder"/>
+        <customObject id="-3" userLabel="Application" customClass="NSObject"/>
+        <window title="Options" allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" hidesOnDeactivate="YES" oneShot="NO" releasedWhenClosed="NO" showsToolbarButton="NO" visibleAtLaunch="NO" frameAutosaveName="" animationBehavior="default" id="ota-g7-hOL" customClass="MachinePanel" customModule="Clock_Signal" customModuleProvider="target">
+            <windowStyleMask key="styleMask" titled="YES" closable="YES" utility="YES" nonactivatingPanel="YES" HUD="YES"/>
+            <windowPositionMask key="initialPositionMask" leftStrut="YES" rightStrut="YES" topStrut="YES" bottomStrut="YES"/>
+            <rect key="contentRect" x="83" y="102" width="200" height="54"/>
+            <rect key="screenRect" x="0.0" y="0.0" width="1366" height="768"/>
+            <view key="contentView" id="7Pv-WL-2Rq">
+                <rect key="frame" x="0.0" y="0.0" width="200" height="54"/>
+                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                <subviews>
+                    <button translatesAutoresizingMaskIntoConstraints="NO" id="sBT-cU-h7s">
+                        <rect key="frame" x="18" y="18" width="164" height="18"/>
+                        <buttonCell key="cell" type="check" title="Load Tapes Quickly" bezelStyle="regularSquare" imagePosition="left" alignment="left" state="on" inset="2" id="w0l-ha-esm">
+                            <behavior key="behavior" changeContents="YES" doesNotDimImage="YES" lightByContents="YES"/>
+                            <font key="font" metaFont="system"/>
+                        </buttonCell>
+                        <connections>
+                            <action selector="setFastLoading:" target="ota-g7-hOL" id="me0-h2-Ga5"/>
+                        </connections>
+                    </button>
+                </subviews>
+                <constraints>
+                    <constraint firstAttribute="trailing" secondItem="sBT-cU-h7s" secondAttribute="trailing" constant="20" id="79b-2A-2c7"/>
+                    <constraint firstItem="sBT-cU-h7s" firstAttribute="top" secondItem="7Pv-WL-2Rq" secondAttribute="top" constant="20" id="E5m-wo-X92"/>
+                    <constraint firstAttribute="bottom" secondItem="sBT-cU-h7s" secondAttribute="bottom" constant="20" id="eZe-Eu-INg"/>
+                    <constraint firstItem="sBT-cU-h7s" firstAttribute="leading" secondItem="7Pv-WL-2Rq" secondAttribute="leading" constant="20" id="nDy-Xc-Ug9"/>
+                </constraints>
+            </view>
+            <connections>
+                <outlet property="fastLoadingButton" destination="sBT-cU-h7s" id="uWa-EB-mbd"/>
+            </connections>
+            <point key="canvasLocation" x="-2" y="-8"/>
+        </window>
+    </objects>
+</document>
--- a/OSBindings/Mac/Clock
+++ b/OSBindings/Mac/Clock
@ -104,7 +104,7 @@
 			<key>CFBundleTypeName</key>
 			<string>Commodore Disk</string>
 			<key>CFBundleTypeRole</key>
-			<string>Viewer</string>
+			<string>Editor</string>
 			<key>LSTypeIsPackage</key>
 			<integer>0</integer>
 			<key>NSDocumentClass</key>
@ -120,7 +120,7 @@
 			<key>CFBundleTypeName</key>
 			<string>Commodore 1540/1 Disk</string>
 			<key>CFBundleTypeRole</key>
-			<string>Viewer</string>
+			<string>Editor</string>
 			<key>LSTypeIsPackage</key>
 			<integer>0</integer>
 			<key>NSDocumentClass</key>
@ -140,7 +140,7 @@
 			<key>CFBundleTypeName</key>
 			<string>Electron/BBC Disk Image</string>
 			<key>CFBundleTypeRole</key>
-			<string>Viewer</string>
+			<string>Editor</string>
 			<key>NSDocumentClass</key>
 			<string>$(PRODUCT_MODULE_NAME).MachineDocument</string>
 		</dict>
@ -154,6 +154,36 @@
 			<key>CFBundleTypeName</key>
 			<string>Disk Image</string>
 			<key>CFBundleTypeRole</key>
+			<string>Editor</string>
+			<key>NSDocumentClass</key>
+			<string>$(PRODUCT_MODULE_NAME).MachineDocument</string>
+		</dict>
+		<dict>
+			<key>CFBundleTypeExtensions</key>
+			<array>
+				<string>o</string>
+				<string>80</string>
+			</array>
+			<key>CFBundleTypeIconFile</key>
+			<string>cassette</string>
+			<key>CFBundleTypeName</key>
+			<string>ZX80 Tape Image</string>
+			<key>CFBundleTypeRole</key>
+			<string>Viewer</string>
+			<key>NSDocumentClass</key>
+			<string>$(PRODUCT_MODULE_NAME).MachineDocument</string>
+		</dict>
+		<dict>
+			<key>CFBundleTypeExtensions</key>
+			<array>
+				<string>p</string>
+				<string>81</string>
+			</array>
+			<key>CFBundleTypeIconFile</key>
+			<string>cassette</string>
+			<key>CFBundleTypeName</key>
+			<string>ZX81 Tape Image</string>
+			<key>CFBundleTypeRole</key>
 			<string>Viewer</string>
 			<key>NSDocumentClass</key>
 			<string>$(PRODUCT_MODULE_NAME).MachineDocument</string>
--- a/Signal/Machine/StaticAnalyser/CSStaticAnalyser.mm
+++ b/Signal/Machine/StaticAnalyser/CSStaticAnalyser.mm
@ -18,6 +18,7 @@
 #import "CSElectron.h"
 #import "CSOric.h"
 #import "CSVic20.h"
+#import "CSZX8081.h"

 #import "Clock_Signal-Swift.h"

@ -49,6 +50,7 @@
 		case StaticAnalyser::Target::Electron:	return @"ElectronOptions";
 		case StaticAnalyser::Target::Oric:		return @"OricOptions";
 		case StaticAnalyser::Target::Vic20:		return @"Vic20Options";
+		case StaticAnalyser::Target::ZX8081:	return @"ZX8081Options";
 		default: return nil;
 	}
 }
@ -61,6 +63,7 @@
 		case StaticAnalyser::Target::Electron:	return [[CSElectron alloc] init];
 		case StaticAnalyser::Target::Oric:		return [[CSOric alloc] init];
 		case StaticAnalyser::Target::Vic20:		return [[CSVic20 alloc] init];
+		case StaticAnalyser::Target::ZX8081:	return [[CSZX8081 alloc] init];
 		default: return nil;
 	}
 }
--- a/Signal/Machine/Wrappers/CSZX8081.h
+++ b/Signal/Machine/Wrappers/CSZX8081.h
@ -0,0 +1,17 @@
+//
+//  CSZX8081.h
+//  Clock Signal
+//
+//  Created by Thomas Harte on 04/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#import "CSMachine.h"
+#import "CSKeyboardMachine.h"
+#import "CSFastLoading.h"
+
+@interface CSZX8081 : CSMachine <CSKeyboardMachine, CSFastLoading>
+
+@property (nonatomic, assign) BOOL useFastLoadingHack;
+
+@end
--- a/Signal/Machine/Wrappers/CSZX8081.mm
+++ b/Signal/Machine/Wrappers/CSZX8081.mm
@ -0,0 +1,104 @@
+//
+//  CSZX8081.m
+//  Clock Signal
+//
+//  Created by Thomas Harte on 04/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#import "CSZX8081.h"
+
+#include "ZX8081.hpp"
+
+#import "CSMachine+Subclassing.h"
+#import "NSData+StdVector.h"
+#import "NSBundle+DataResource.h"
+
+@implementation CSZX8081 {
+	ZX8081::Machine _zx8081;
+}
+
+- (CRTMachine::Machine * const)machine {
+	return &_zx8081;
+}
+
+- (instancetype)init {
+	self = [super init];
+	if(self) {
+		_zx8081.set_rom(ZX8081::ROMType::ZX80, [self rom:@"zx80"].stdVector8);
+		_zx8081.set_rom(ZX8081::ROMType::ZX81, [self rom:@"zx81"].stdVector8);
+	}
+	return self;
+}
+
+- (NSData *)rom:(NSString *)name {
+	return [[NSBundle mainBundle] dataForResource:name withExtension:@"rom" subdirectory:@"ROMImages/ZX8081"];
+}
+
+#pragma mark - Keyboard Mapping
+
+- (void)clearAllKeys {
+	@synchronized(self) {
+		_zx8081.clear_all_keys();
+	}
+}
+
+- (void)setKey:(uint16_t)key isPressed:(BOOL)isPressed {
+	@synchronized(self) {
+		switch(key)
+		{
+			case VK_ANSI_0:		_zx8081.set_key_state(ZX8081::Key::Key0, isPressed);	break;
+			case VK_ANSI_1:		_zx8081.set_key_state(ZX8081::Key::Key1, isPressed);	break;
+			case VK_ANSI_2:		_zx8081.set_key_state(ZX8081::Key::Key2, isPressed);	break;
+			case VK_ANSI_3:		_zx8081.set_key_state(ZX8081::Key::Key3, isPressed);	break;
+			case VK_ANSI_4:		_zx8081.set_key_state(ZX8081::Key::Key4, isPressed);	break;
+			case VK_ANSI_5:		_zx8081.set_key_state(ZX8081::Key::Key5, isPressed);	break;
+			case VK_ANSI_6:		_zx8081.set_key_state(ZX8081::Key::Key6, isPressed);	break;
+			case VK_ANSI_7:		_zx8081.set_key_state(ZX8081::Key::Key7, isPressed);	break;
+			case VK_ANSI_8:		_zx8081.set_key_state(ZX8081::Key::Key8, isPressed);	break;
+			case VK_ANSI_9:		_zx8081.set_key_state(ZX8081::Key::Key9, isPressed);	break;
+
+			case VK_ANSI_Q:		_zx8081.set_key_state(ZX8081::Key::KeyQ, isPressed);	break;
+			case VK_ANSI_W:		_zx8081.set_key_state(ZX8081::Key::KeyW, isPressed);	break;
+			case VK_ANSI_E:		_zx8081.set_key_state(ZX8081::Key::KeyE, isPressed);	break;
+			case VK_ANSI_R:		_zx8081.set_key_state(ZX8081::Key::KeyR, isPressed);	break;
+			case VK_ANSI_T:		_zx8081.set_key_state(ZX8081::Key::KeyT, isPressed);	break;
+			case VK_ANSI_Y:		_zx8081.set_key_state(ZX8081::Key::KeyY, isPressed);	break;
+			case VK_ANSI_U:		_zx8081.set_key_state(ZX8081::Key::KeyU, isPressed);	break;
+			case VK_ANSI_I:		_zx8081.set_key_state(ZX8081::Key::KeyI, isPressed);	break;
+			case VK_ANSI_O:		_zx8081.set_key_state(ZX8081::Key::KeyO, isPressed);	break;
+			case VK_ANSI_P:		_zx8081.set_key_state(ZX8081::Key::KeyP, isPressed);	break;
+
+			case VK_ANSI_A:		_zx8081.set_key_state(ZX8081::Key::KeyA, isPressed);	break;
+			case VK_ANSI_S:		_zx8081.set_key_state(ZX8081::Key::KeyS, isPressed);	break;
+			case VK_ANSI_D:		_zx8081.set_key_state(ZX8081::Key::KeyD, isPressed);	break;
+			case VK_ANSI_F:		_zx8081.set_key_state(ZX8081::Key::KeyF, isPressed);	break;
+			case VK_ANSI_G:		_zx8081.set_key_state(ZX8081::Key::KeyG, isPressed);	break;
+			case VK_ANSI_H:		_zx8081.set_key_state(ZX8081::Key::KeyH, isPressed);	break;
+			case VK_ANSI_J:		_zx8081.set_key_state(ZX8081::Key::KeyJ, isPressed);	break;
+			case VK_ANSI_K:		_zx8081.set_key_state(ZX8081::Key::KeyK, isPressed);	break;
+			case VK_ANSI_L:		_zx8081.set_key_state(ZX8081::Key::KeyL, isPressed);	break;
+
+			case VK_ANSI_Z:		_zx8081.set_key_state(ZX8081::Key::KeyZ, isPressed);	break;
+			case VK_ANSI_X:		_zx8081.set_key_state(ZX8081::Key::KeyX, isPressed);	break;
+			case VK_ANSI_C:		_zx8081.set_key_state(ZX8081::Key::KeyC, isPressed);	break;
+			case VK_ANSI_V:		_zx8081.set_key_state(ZX8081::Key::KeyV, isPressed);	break;
+			case VK_ANSI_B:		_zx8081.set_key_state(ZX8081::Key::KeyB, isPressed);	break;
+			case VK_ANSI_N:		_zx8081.set_key_state(ZX8081::Key::KeyN, isPressed);	break;
+			case VK_ANSI_M:		_zx8081.set_key_state(ZX8081::Key::KeyM, isPressed);	break;
+
+			case VK_Shift:
+			case VK_RightShift:
+								_zx8081.set_key_state(ZX8081::Key::KeyShift, isPressed);	break;
+			break;
+
+			case VK_ANSI_Period:_zx8081.set_key_state(ZX8081::Key::KeyDot, isPressed);		break;
+			case VK_Return:		_zx8081.set_key_state(ZX8081::Key::KeyEnter, isPressed);	break;
+			case VK_Space:		_zx8081.set_key_state(ZX8081::Key::KeySpace, isPressed);	break;
+		}
+	}
+}
+
+- (NSString *)userDefaultsPrefix {	return @"zx8081";	}
+
+@end
--- a/SignalTests/Bridges/TestMachineZ80.h
+++ b/SignalTests/Bridges/TestMachineZ80.h
@ -59,6 +59,7 @@ typedef NS_ENUM(NSInteger, CSTestMachineZ80Register) {
@property(nonatomic, readonly, nonnull) NSArray<CSTestMachineZ80BusOperationCapture *> *busOperationCaptures;

@property(nonatomic, readonly) BOOL isHalted;
+@property(nonatomic, readonly) int completedCycles;

@property(nonatomic) BOOL nmiLine;
@property(nonatomic) BOOL irqLine;
--- a/SignalTests/Bridges/TestMachineZ80.mm
+++ b/SignalTests/Bridges/TestMachineZ80.mm
@ -149,6 +149,10 @@ static CPU::Z80::Register registerForRegister(CSTestMachineZ80Register reg) {
 	return _processor->get_halt_line() ? YES : NO;
 }

+- (int)completedCycles {
+	return _processor->get_length_of_completed_machine_cycles();
+}
+
 - (void)setNmiLine:(BOOL)nmiLine {
 	_nmiLine = nmiLine;
 	_processor->set_non_maskable_interrupt_line(nmiLine ? true : false);
--- a/SignalTests/FUSETests.swift
+++ b/SignalTests/FUSETests.swift
@ -194,6 +194,10 @@ class FUSETests: XCTestCase {

 			machine.runForNumber(ofCycles: Int32(targetState.tStates))

+			// Verify that exactly the right number of cycles was hit; this is a primitive cycle length tester.
+			let cyclesRun = machine.completedCycles
+			XCTAssert(cyclesRun == Int32(targetState.tStates), "Instruction length off; was \(machine.completedCycles) but should be \(targetState.tStates): \(name)")
+
 			let finalState = RegisterState(machine: machine)

 			// Compare processor state.
--- a/SignalTests/Z80InterruptTests.swift
+++ b/SignalTests/Z80InterruptTests.swift
@ -135,8 +135,13 @@ class Z80InterruptTests: XCTestCase {
 		machine.runForNumber(ofCycles: 4)
 		XCTAssertEqual(machine.value(for: .programCounter), 0x0102)

-		// run for eleven more cycles to allow the IRQ to begin
-		machine.runForNumber(ofCycles: 13)
+		// run for twelve cycles and confirm that the IRQ has yet to begin
+		machine.runForNumber(ofCycles: 12)
+
+		XCTAssertNotEqual(machine.value(for: .programCounter), 0x38)
+
+		// run for one more cycles to allow the IRQ to begin
+		machine.runForNumber(ofCycles: 1)

 		// confirm that the PC is now at 0x38, that the old is on the stack and
 		// that interrupts are now disabled
--- a/Processors/Z80/Z80.hpp
+++ b/Processors/Z80/Z80.hpp
@ -38,7 +38,7 @@ enum Register {

 	IXh,	IXl,	IX,
 	IYh,	IYl,	IY,
-	R,		I,
+	R,		I,		Refresh,

 	IFF1,	IFF2,	IM
 };
@ -285,6 +285,13 @@ template <class T> class Processor {
 				Program(INDEX(), FETCHL(temp8_, INDEX_ADDR()), {MicroOp::op, &temp8_}),	\
 				Program({MicroOp::op, &a_})

+#define READ_OP_GROUP_D(op)	\
+				Program({MicroOp::op, &bc_.bytes.high}),	Program({MicroOp::op, &bc_.bytes.low}),	\
+				Program({MicroOp::op, &de_.bytes.high}),	Program({MicroOp::op, &de_.bytes.low}),	\
+				Program({MicroOp::op, &index.bytes.high}),	Program({MicroOp::op, &index.bytes.low}),	\
+				Program(INDEX(), FETCHL(temp8_, INDEX_ADDR()), WAIT(1), {MicroOp::op, &temp8_}),	\
+				Program({MicroOp::op, &a_})
+
 #define RMW(x, op, ...) Program(INDEX(), FETCHL(x, INDEX_ADDR()), {MicroOp::op, &x}, WAIT(1), STOREL(x, INDEX_ADDR()))
 #define RMWI(x, op, ...) Program(WAIT(2), FETCHL(x, INDEX_ADDR()), {MicroOp::op, &x}, WAIT(1), STOREL(x, INDEX_ADDR()))

@ -345,7 +352,7 @@ template <class T> class Processor {

 			// Copy in all programs and set pointers.
 			size_t destination = 0;
-			for(int c = 0; c < 256; c++) {
+			for(size_t c = 0; c < 256; c++) {
 				target.instructions[c] = &target.all_operations[destination];
 				for(int t = 0; t < lengths[c];) {
 					// Skip zero-length bus cycles.
@ -385,19 +392,19 @@ template <class T> class Processor {
 				/* 0x40 IN B, (C);	0x41 OUT (C), B */	IN_OUT(bc_.bytes.high),
 				/* 0x42 SBC HL, BC */	SBC16(hl_, bc_),				/* 0x43 LD (nn), BC */	Program(FETCH16(temp16_, pc_), STORE16L(bc_, temp16_)),
 				/* 0x44 NEG */			Program({MicroOp::NEG}),		/* 0x45 RETN */			Program(POP(pc_), {MicroOp::RETN}),
-				/* 0x46 IM 0 */			Program({MicroOp::IM}),			/* 0x47 LD I, A */		LD(i_, a_),
+				/* 0x46 IM 0 */			Program({MicroOp::IM}),			/* 0x47 LD I, A */		Program(WAIT(1), {MicroOp::Move8, &a_, &i_}),
 				/* 0x40 IN B, (C);	0x41 OUT (C), B */	IN_OUT(bc_.bytes.low),
 				/* 0x4a ADC HL, BC */	ADC16(hl_, bc_),				/* 0x4b LD BC, (nn) */	Program(FETCH16(temp16_, pc_), FETCH16L(bc_, temp16_)),
 				/* 0x4c NEG */			Program({MicroOp::NEG}),		/* 0x4d RETI */			Program(POP(pc_), {MicroOp::RETN}),
-				/* 0x4e IM 0/1 */		Program({MicroOp::IM}),			/* 0x4f LD R, A */		LD(r_, a_),
+				/* 0x4e IM 0/1 */		Program({MicroOp::IM}),			/* 0x4f LD R, A */		Program(WAIT(1), {MicroOp::Move8, &a_, &r_}),
 				/* 0x40 IN B, (C);	0x41 OUT (C), B */	IN_OUT(de_.bytes.high),
 				/* 0x52 SBC HL, DE */	SBC16(hl_, de_),				/* 0x53 LD (nn), DE */	Program(FETCH16(temp16_, pc_), STORE16L(de_, temp16_)),
 				/* 0x54 NEG */			Program({MicroOp::NEG}),		/* 0x55 RETN */			Program(POP(pc_), {MicroOp::RETN}),
-				/* 0x56 IM 1 */			Program({MicroOp::IM}),			/* 0x57 LD A, I */		Program({MicroOp::Move8, &i_, &a_}, {MicroOp::SetAFlags}),
+				/* 0x56 IM 1 */			Program({MicroOp::IM}),			/* 0x57 LD A, I */		Program(WAIT(1), {MicroOp::Move8, &i_, &a_}, {MicroOp::SetAFlags}),
 				/* 0x40 IN B, (C);	0x41 OUT (C), B */	IN_OUT(de_.bytes.low),
 				/* 0x5a ADC HL, DE */	ADC16(hl_, de_),				/* 0x5b LD DE, (nn) */	Program(FETCH16(temp16_, pc_), FETCH16L(de_, temp16_)),
 				/* 0x5c NEG */			Program({MicroOp::NEG}),		/* 0x5d RETN */			Program(POP(pc_), {MicroOp::RETN}),
-				/* 0x5e IM 2 */			Program({MicroOp::IM}),			/* 0x5f LD A, R */		Program({MicroOp::Move8, &r_, &a_}, {MicroOp::SetAFlags}),
+				/* 0x5e IM 2 */			Program({MicroOp::IM}),			/* 0x5f LD A, R */		Program(WAIT(1), {MicroOp::Move8, &r_, &a_}, {MicroOp::SetAFlags}),
 				/* 0x40 IN B, (C);	0x41 OUT (C), B */	IN_OUT(hl_.bytes.high),
 				/* 0x62 SBC HL, HL */	SBC16(hl_, hl_),				/* 0x63 LD (nn), HL */	Program(FETCH16(temp16_, pc_), STORE16L(hl_, temp16_)),
 				/* 0x64 NEG */			Program({MicroOp::NEG}),		/* 0x65 RETN */			Program(POP(pc_), {MicroOp::RETN}),
@ -461,7 +468,7 @@ template <class T> class Processor {
 				/* 0x40 – 0x7f: BIT */
 				/* 0x80 – 0xcf: RES */
 				/* 0xd0 – 0xdf: SET */
-				CB_PAGE(MODIFY_OP_GROUP, READ_OP_GROUP)
+				CB_PAGE(MODIFY_OP_GROUP, READ_OP_GROUP_D)
 			};
 			InstructionTable offsets_cb_program_table = {
 				CB_PAGE(IX_MODIFY_OP_GROUP, IX_READ_OP_GROUP)
@ -775,7 +782,10 @@ template <class T> class Processor {
 				while(bus_request_line_) {
 					static MachineCycle bus_acknowledge_cycle = {BusOperation::BusAcknowledge, 1};
 					number_of_cycles_ -= static_cast<T *>(this)->perform_machine_cycle(bus_acknowledge_cycle) + 1;
-					if(!number_of_cycles_) return;
+					if(!number_of_cycles_) {
+						static_cast<T *>(this)->flush();
+						return;
+					}
 				}

 				while(!bus_request_line_) {
@ -783,14 +793,18 @@ template <class T> class Processor {
 					scheduled_program_counter_++;

 #define set_parity(v)	\
-	parity_overflow_result_ = v^1;\
+	parity_overflow_result_ = (uint8_t)(v^1);\
 	parity_overflow_result_ ^= parity_overflow_result_ >> 4;\
 	parity_overflow_result_ ^= parity_overflow_result_ << 2;\
 	parity_overflow_result_ ^= parity_overflow_result_ >> 1;

 					switch(operation->type) {
 						case MicroOp::BusOperation:
-							if(number_of_cycles_ < operation->machine_cycle.length) { scheduled_program_counter_--; return; }
+							if(number_of_cycles_ < operation->machine_cycle.length) {
+								scheduled_program_counter_--;
+								static_cast<T *>(this)->flush();
+								return;
+							}
 							number_of_cycles_ -= operation->machine_cycle.length;
 							last_request_status_ = request_status_;
 							number_of_cycles_ -= static_cast<T *>(this)->perform_machine_cycle(operation->machine_cycle);
@ -800,7 +814,7 @@ template <class T> class Processor {
 						break;
 						case MicroOp::DecodeOperation:
 							r_ = (r_ & 0x80) | ((r_ + current_instruction_page_->r_step) & 0x7f);
-							pc_.full += pc_increment_;
+							pc_.full += pc_increment_ & (uint16_t)halt_mask_;
 						case MicroOp::DecodeOperationNoRChange:
 							scheduled_program_counter_ = current_instruction_page_->instructions[operation_ & halt_mask_];
 						break;
@ -854,7 +868,7 @@ template <class T> class Processor {
 						break;

 						case MicroOp::CCF:
-							half_carry_result_ = carry_result_ << 4;
+							half_carry_result_ = (uint8_t)(carry_result_ << 4);
 							carry_result_ ^= Flag::Carry;
 							subtract_flag_ = 0;
 							bit53_result_ = a_;
@ -884,9 +898,9 @@ template <class T> class Processor {

 #define set_arithmetic_flags(sub, b53)	\
 	sign_result_ = zero_result_ = (uint8_t)result;	\
-	carry_result_ = result >> 8;	\
-	half_carry_result_ = half_result;	\
-	parity_overflow_result_ = overflow >> 5;	\
+	carry_result_ = (uint8_t)(result >> 8);	\
+	half_carry_result_ = (uint8_t)half_result;	\
+	parity_overflow_result_ = (uint8_t)(overflow >> 5);	\
 	subtract_flag_ = sub;	\
 	bit53_result_ = (uint8_t)b53;

@ -966,8 +980,8 @@ template <class T> class Processor {
 							bit53_result_ = sign_result_ = zero_result_ = a_;
 							parity_overflow_result_ = overflow ? Flag::Overflow : 0;
 							subtract_flag_ = Flag::Subtract;
-							carry_result_ = result >> 8;
-							half_carry_result_ = halfResult;
+							carry_result_ = (uint8_t)(result >> 8);
+							half_carry_result_ = (uint8_t)halfResult;
 						} break;

 						case MicroOp::Increment8: {
@ -983,8 +997,8 @@ template <class T> class Processor {

 							// sign, zero and 5 & 3 are set directly from the result
 							bit53_result_ = sign_result_ = zero_result_ = (uint8_t)result;
-							half_carry_result_ = half_result;
-							parity_overflow_result_ = overflow >> 5;
+							half_carry_result_ = (uint8_t)half_result;
+							parity_overflow_result_ = (uint8_t)(overflow >> 5);
 							subtract_flag_ = 0;
 						} break;

@ -1001,8 +1015,8 @@ template <class T> class Processor {

 							// sign, zero and 5 & 3 are set directly from the result
 							bit53_result_ = sign_result_ = zero_result_ = (uint8_t)result;
-							half_carry_result_ = half_result;
-							parity_overflow_result_ = overflow >> 5;
+							half_carry_result_ = (uint8_t)half_result;
+							parity_overflow_result_ = (uint8_t)(overflow >> 5);
 							subtract_flag_ = Flag::Subtract;
 						} break;

@ -1071,8 +1085,8 @@ template <class T> class Processor {
 							int halfResult = (sourceValue&0xfff) + (destinationValue&0xfff);

 							bit53_result_ = (uint8_t)(result >> 8);
-							carry_result_ = result >> 16;
-							half_carry_result_ = (halfResult >> 8);
+							carry_result_ = (uint8_t)(result >> 16);
+							half_carry_result_ = (uint8_t)(halfResult >> 8);
 							subtract_flag_ = 0;

 							*(uint16_t *)operation->destination = (uint16_t)result;
@ -1091,9 +1105,9 @@ template <class T> class Processor {
 							sign_result_	= (uint8_t)(result >> 8);
 							zero_result_	= (uint8_t)(result | sign_result_);
 							subtract_flag_	= 0;
-							carry_result_	= result >> 16;
-							half_carry_result_ = halfResult >> 8;
-							parity_overflow_result_ = overflow >> 13;
+							carry_result_	= (uint8_t)(result >> 16);
+							half_carry_result_ = (uint8_t)(halfResult >> 8);
+							parity_overflow_result_ = (uint8_t)(overflow >> 13);

 							*(uint16_t *)operation->destination = (uint16_t)result;
 						} break;
@ -1114,9 +1128,9 @@ template <class T> class Processor {
 							sign_result_	= (uint8_t)(result >> 8);
 							zero_result_	= (uint8_t)(result | sign_result_);
 							subtract_flag_	= Flag::Subtract;
-							carry_result_	= result >> 16;
-							half_carry_result_ = halfResult >> 8;
-							parity_overflow_result_ = overflow >> 13;
+							carry_result_	= (uint8_t)(result >> 16);
+							half_carry_result_ = (uint8_t)(halfResult >> 8);
+							parity_overflow_result_ = (uint8_t)(overflow >> 13);

 							*(uint16_t *)operation->destination = (uint16_t)result;
 						} break;
@ -1173,7 +1187,7 @@ template <class T> class Processor {
 	de_.full += dir;	\
 	hl_.full += dir;	\
 	uint8_t sum = a_ + temp8_;	\
-	bit53_result_ = (sum&0x8) | ((sum & 0x02) << 4);	\
+	bit53_result_ = (uint8_t)((sum&0x8) | ((sum & 0x02) << 4));	\
 	subtract_flag_ = 0;	\
 	half_carry_result_ = 0;	\
 	parity_overflow_result_ = bc_.full ? Flag::Parity : 0;
@ -1438,7 +1452,7 @@ template <class T> class Processor {
 							memptr_.full = hl_.full + 1;
 							uint8_t low_nibble = a_ & 0xf;
 							a_ = (a_ & 0xf0) | (temp8_ & 0xf);
-							temp8_ = (temp8_ >> 4) | (low_nibble << 4);
+							temp8_ = (uint8_t)((temp8_ >> 4) | (low_nibble << 4));
 							set_decimal_rotate_flags();
 						} break;

@ -1446,7 +1460,7 @@ template <class T> class Processor {
 							memptr_.full = hl_.full + 1;
 							uint8_t low_nibble = a_ & 0xf;
 							a_ = (a_ & 0xf0) | (temp8_ >> 4);
-							temp8_ = (temp8_ << 4) | low_nibble;
+							temp8_ = (uint8_t)((temp8_ << 4) | low_nibble);
 							set_decimal_rotate_flags();
 						} break;

@ -1541,7 +1555,7 @@ template <class T> class Processor {
 						break;

 						case MicroOp::CalculateIndexAddress:
-							memptr_.full = *(uint16_t *)operation->source + (int8_t)temp8_;
+							memptr_.full = (uint16_t)(*(uint16_t *)operation->source + (int8_t)temp8_);
 						break;

 						case MicroOp::IndexedPlaceHolder:
@ -1649,10 +1663,11 @@ template <class T> class Processor {

 				case Register::R:						return r_;
 				case Register::I:						return i_;
+				case Register::Refresh:					return (uint16_t)(r_ |	(i_ << 8));

 				case Register::IFF1:					return iff1_ ? 1 : 0;
 				case Register::IFF2:					return iff2_ ? 1 : 0;
-				case Register::IM:						return interrupt_mode_;
+				case Register::IM:						return (uint16_t)interrupt_mode_;

 				default: return 0;
 			}
@ -1707,6 +1722,7 @@ template <class T> class Processor {

 				case Register::R:				r_ = (uint8_t)value;					break;
 				case Register::I:				i_ = (uint8_t)value;					break;
+				case Register::Refresh:			r_ = (uint8_t)value;	i_ = (uint8_t)(value >> 8);		break;

 				case Register::IFF1:			iff1_ = !!value;						break;
 				case Register::IFF2:			iff2_ = !!value;						break;
@ -1725,8 +1741,14 @@ template <class T> class Processor {

 		/*!
 			Sets the logical value of the interrupt line.
+
+			@param offset If called while within perform_machine_cycle this may be a value indicating
+			how many cycles before now the line changed state. The value may not be longer than the
+			current machine cycle. If called at any other time, this must be zero.
 		*/
-		void set_interrupt_line(bool value) {
+		void set_interrupt_line(bool value, int offset = 0) {
+			if(irq_line_ == value) return;
+
 			// IRQ requests are level triggered and masked.
 			irq_line_ = value;
 			if(irq_line_ && iff1_) {
@ -1734,14 +1756,28 @@ template <class T> class Processor {
 			} else {
 				request_status_ &= ~Interrupt::IRQ;
 			}
+
+			// If this change happened at least one cycle ago then: (i) we're promised that this is a machine
+			// cycle per the contract on supplying an offset; and (ii) that means it happened before the lines
+			// were sampled. So adjust the most recent sample.
+			if(offset < 0) {
+				last_request_status_ = (last_request_status_ & ~Interrupt::IRQ) | (request_status_ & Interrupt::IRQ);
+			}
 		}

 		/*!
 			Sets the logical value of the non-maskable interrupt line.
+			
+			@param offset See discussion in set_interrupt_line.
 		*/
-		void set_non_maskable_interrupt_line(bool value) {
+		void set_non_maskable_interrupt_line(bool value, int offset = 0) {
 			// NMIs are edge triggered and cannot be masked.
-			if(value) request_status_ |= Interrupt::NMI;
+			if(value) {
+				request_status_ |= Interrupt::NMI;
+				if(offset < 0) {
+					last_request_status_ |= Interrupt::NMI;
+				}
+			}
 		}

 		/*!
--- a/Processors/Z80/Z80AllRAM.cpp
+++ b/Processors/Z80/Z80AllRAM.cpp
@ -14,9 +14,10 @@ namespace {

 class ConcreteAllRAMProcessor: public AllRAMProcessor, public Processor<ConcreteAllRAMProcessor> {
 	public:
-		ConcreteAllRAMProcessor() : AllRAMProcessor() {}
+		ConcreteAllRAMProcessor() : AllRAMProcessor(), completed_cycles(0) {}

 		inline int perform_machine_cycle(const MachineCycle &cycle) {
+			completed_cycles += cycle.length;
 			uint16_t address = cycle.address ? *cycle.address : 0x0000;
 			switch(cycle.operation) {
 				case BusOperation::ReadOpcode:
@ -88,6 +89,14 @@ class ConcreteAllRAMProcessor: public AllRAMProcessor, public Processor<Concrete
 		void set_non_maskable_interrupt_line(bool value) {
 			CPU::Z80::Processor<ConcreteAllRAMProcessor>::set_non_maskable_interrupt_line(value);
 		}
+
+		int get_length_of_completed_machine_cycles() {
+			return completed_cycles;
+		}
+
+		private:
+			int completed_cycles;
+
 };

 }
--- a/Processors/Z80/Z80AllRAM.hpp
+++ b/Processors/Z80/Z80AllRAM.hpp
@ -36,6 +36,8 @@ class AllRAMProcessor:
 		virtual void set_interrupt_line(bool value) = 0;
 		virtual void set_non_maskable_interrupt_line(bool value) = 0;

+		virtual int get_length_of_completed_machine_cycles() = 0;
+
 	protected:
 		MemoryAccessDelegate *delegate_;
 		AllRAMProcessor() : ::CPU::AllRAMProcessor(65536), delegate_(nullptr) {}
--- a/ROMImages/ZX8081/readme.txt
+++ b/ROMImages/ZX8081/readme.txt
@ -0,0 +1,6 @@
+ROM files would ordinarily go here; the copyright status of these is uncertain so they have not been included in this repository.
+
+Expected files:
+
+zx80.rom
+zx81.rom
--- a/StaticAnalyser/StaticAnalyser.cpp
+++ b/StaticAnalyser/StaticAnalyser.cpp
@ -15,6 +15,7 @@
 #include "Atari/StaticAnalyser.hpp"
 #include "Commodore/StaticAnalyser.hpp"
 #include "Oric/StaticAnalyser.hpp"
+#include "ZX8081/StaticAnalyser.hpp"

 // Cartridges
 #include "../Storage/Cartridge/Formats/BinaryDump.hpp"
@ -32,13 +33,15 @@
 #include "../Storage/Tape/Formats/OricTAP.hpp"
 #include "../Storage/Tape/Formats/TapePRG.hpp"
 #include "../Storage/Tape/Formats/TapeUEF.hpp"
+#include "../Storage/Tape/Formats/ZX80O81P.hpp"

 typedef int TargetPlatformType;
 enum class TargetPlatform: TargetPlatformType {
 	Acorn		=	1 << 0,
 	Atari2600	=	1 << 1,
 	Commodore	=	1 << 2,
-	Oric		=	1 << 3
+	Oric		=	1 << 3,
+	ZX8081		=	1 << 4,
 };

 using namespace StaticAnalyser;
@ -86,6 +89,8 @@ std::list<Target> StaticAnalyser::GetTargets(const char *file_name)

 	if(lowercase_extension)
 	{
+		Format("80", tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)						// 80
+		Format("81", tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)						// 81
 		Format("a26", cartridges, Cartridge::BinaryDump, TargetPlatform::Atari2600)		// A26
 		Format("adf", disks, Disk::AcornADF, TargetPlatform::Acorn)						// ADF
 		Format("bin", cartridges, Cartridge::BinaryDump, TargetPlatform::Atari2600)		// BIN
@ -93,6 +98,8 @@ std::list<Target> StaticAnalyser::GetTargets(const char *file_name)
 		Format("dsd", disks, Disk::SSD, TargetPlatform::Acorn)							// DSD
 		Format("dsk", disks, Disk::OricMFMDSK, TargetPlatform::Oric)					// DSK
 		Format("g64", disks, Disk::G64, TargetPlatform::Commodore)						// G64
+		Format("o", tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)						// O
+		Format("p", tapes, Tape::ZX80O81P, TargetPlatform::ZX8081)						// O

 		// PRG
 		if(!strcmp(lowercase_extension, "prg"))
@ -125,6 +132,7 @@ std::list<Target> StaticAnalyser::GetTargets(const char *file_name)
 		if(potential_platforms & (TargetPlatformType)TargetPlatform::Atari2600)	Atari::AddTargets(disks, tapes, cartridges, targets);
 		if(potential_platforms & (TargetPlatformType)TargetPlatform::Commodore)	Commodore::AddTargets(disks, tapes, cartridges, targets);
 		if(potential_platforms & (TargetPlatformType)TargetPlatform::Oric)		Oric::AddTargets(disks, tapes, cartridges, targets);
+		if(potential_platforms & (TargetPlatformType)TargetPlatform::ZX8081)	ZX8081::AddTargets(disks, tapes, cartridges, targets);

 		free(lowercase_extension);
 	}
--- a/StaticAnalyser/StaticAnalyser.hpp
+++ b/StaticAnalyser/StaticAnalyser.hpp
@ -40,6 +40,12 @@ enum class Atari2600PagingModel {
 	Pitfall2
 };

+enum class ZX8081MemoryModel {
+	Unexpanded,
+	SixteenKB,
+	SixtyFourKB
+};
+
 /*!
 	A list of disks, tapes and cartridges plus information about the machine to which to attach them and its configuration,
 	and instructions on how to launch the software attached, plus a measure of confidence in this target's correctness.
@ -49,7 +55,8 @@ struct Target {
 		Atari2600,
 		Electron,
 		Vic20,
-		Oric
+		Oric,
+		ZX8081
 	} machine;
 	float probability;

@ -74,6 +81,11 @@ struct Target {
 			Vic20MemoryModel memory_model;
 			bool has_c1540;
 		} vic20;
+
+		struct {
+			ZX8081MemoryModel memory_model;
+			bool isZX81;
+		} zx8081;
 	};

 	std::string loadingCommand;
--- a/StaticAnalyser/ZX8081/StaticAnalyser.cpp
+++ b/StaticAnalyser/ZX8081/StaticAnalyser.cpp
@ -0,0 +1,53 @@
+//
+//  StaticAnalyser.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 04/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#include "StaticAnalyser.hpp"
+
+#include <string>
+#include <vector>
+
+#include "../../Storage/Tape/Parsers/ZX8081.hpp"
+
+static std::vector<Storage::Data::ZX8081::File> GetFiles(const std::shared_ptr<Storage::Tape::Tape> &tape) {
+	std::vector<Storage::Data::ZX8081::File> files;
+	Storage::Tape::ZX8081::Parser parser;
+
+	while(!tape->is_at_end()) {
+		std::shared_ptr<Storage::Data::ZX8081::File> next_file = parser.get_next_file(tape);
+		if(next_file != nullptr) {
+			files.push_back(*next_file);
+		}
+	}
+
+	return files;
+}
+
+void StaticAnalyser::ZX8081::AddTargets(
+		const std::list<std::shared_ptr<Storage::Disk::Disk>> &disks,
+		const std::list<std::shared_ptr<Storage::Tape::Tape>> &tapes,
+		const std::list<std::shared_ptr<Storage::Cartridge::Cartridge>> &cartridges,
+		std::list<StaticAnalyser::Target> &destination) {
+
+	if(!tapes.empty()) {
+		std::vector<Storage::Data::ZX8081::File> files = GetFiles(tapes.front());
+		if(!files.empty()) {
+			StaticAnalyser::Target target;
+			target.machine = Target::ZX8081;
+			target.zx8081.isZX81 = files.front().isZX81;
+			if(files.front().data.size() > 16384) {
+				target.zx8081.memory_model = ZX8081MemoryModel::SixtyFourKB;
+			} else if(files.front().data.size() > 1024) {
+				target.zx8081.memory_model = ZX8081MemoryModel::SixteenKB;
+			} else {
+				target.zx8081.memory_model = ZX8081MemoryModel::Unexpanded;
+			}
+			target.tapes = tapes;
+			destination.push_back(target);
+		}
+	}
+}
--- a/StaticAnalyser/ZX8081/StaticAnalyser.hpp
+++ b/StaticAnalyser/ZX8081/StaticAnalyser.hpp
@ -0,0 +1,27 @@
+//
+//  StaticAnalyser.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 04/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#ifndef StaticAnalyser_ZX8081_StaticAnalyser_hpp
+#define StaticAnalyser_ZX8081_StaticAnalyser_hpp
+
+#include "../StaticAnalyser.hpp"
+
+namespace StaticAnalyser {
+namespace ZX8081 {
+
+void AddTargets(
+	const std::list<std::shared_ptr<Storage::Disk::Disk>> &disks,
+	const std::list<std::shared_ptr<Storage::Tape::Tape>> &tapes,
+	const std::list<std::shared_ptr<Storage::Cartridge::Cartridge>> &cartridges,
+	std::list<Target> &destination
+);
+
+}
+}
+
+#endif /* StaticAnalyser_hpp */
--- a/Storage/Data/ZX8081.cpp
+++ b/Storage/Data/ZX8081.cpp
@ -0,0 +1,127 @@
+//
+//  ZX8081.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 08/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#include "ZX8081.hpp"
+
+using namespace Storage::Data::ZX8081;
+
+static uint16_t short_at(size_t address, const std::vector<uint8_t> &data) {
+	return (uint16_t)(data[address] | (data[address + 1] << 8));
+}
+
+static std::shared_ptr<File> ZX80FileFromData(const std::vector<uint8_t> &data) {
+	// Does this look like a ZX80 file?
+
+	if(data.size() < 0x28) return nullptr;
+
+//	uint16_t next_line_number = short_at(0x2, data);
+//	uint16_t first_visible_line = short_at(0x13, data);
+
+	uint16_t vars = short_at(0x8, data);
+	uint16_t end_of_file = short_at(0xa, data);
+	uint16_t display_address = short_at(0xc, data);
+
+	// check that the end of file is contained within the supplied data
+	if(end_of_file - 0x4000 > data.size()) return nullptr;
+
+	// check for the proper ordering of buffers
+	if(vars > end_of_file) return nullptr;
+	if(end_of_file > display_address) return nullptr;
+
+	// TODO: does it make sense to inspect the tokenised BASIC?
+	// It starts at 0x4028 and proceeds as [16-bit line number] [tokens] [0x76],
+	// but I'm as yet unable to find documentation of the tokens.
+
+	// TODO: check that the line numbers declared above exist (?)
+
+	std::shared_ptr<File> file(new File);
+	file->data = data;
+	file->isZX81 = false;
+	return file;
+}
+
+static std::shared_ptr<File> ZX81FileFromData(const std::vector<uint8_t> &data) {
+	// Does this look like a ZX81 file?
+
+	// Look for a file name.
+	size_t data_pointer = 0;
+	int c = 11;
+	while(c--) {
+		if(data[data_pointer] & 0x80) break;
+		data_pointer++;
+	}
+	if(!c) return nullptr;
+	data_pointer++;
+
+	if(data.size() < data_pointer + 0x405e - 0x4009) return nullptr;
+
+	if(data[data_pointer]) return nullptr;
+
+	uint16_t vars = short_at(data_pointer + 0x4010 - 0x4009, data);
+	uint16_t end_of_file = short_at(data_pointer + 0x4014 - 0x4009, data);
+//	uint16_t display_address = short_at(0x400c - 0x4009, data);
+
+	// check that the end of file is contained within the supplied data
+	if(data_pointer + end_of_file - 0x4009 > data.size()) return nullptr;
+
+	// check for the proper ordering of buffers
+	if(vars > end_of_file) return nullptr;
+//	if(end_of_file > display_address) return nullptr;
+
+	// TODO: does it make sense to inspect the tokenised BASIC?
+	// It starts at 0x4028 and proceeds as [16-bit line number] [tokens] [0x76],
+	// but I'm as yet unable to find documentation of the tokens.
+
+	// TODO: check that the line numbers declared above exist (?)
+
+	std::shared_ptr<File> file(new File);
+	file->data = data;
+	file->isZX81 = true;
+	return file;
+}
+
+std::shared_ptr<File> Storage::Data::ZX8081::FileFromData(const std::vector<uint8_t> &data) {
+	std::shared_ptr<Storage::Data::ZX8081::File> result = ZX80FileFromData(data);
+	if(result) return result;
+	return ZX81FileFromData(data);
+}
+
+#pragma mark - String conversion
+
+std::wstring Storage::Data::ZX8081::StringFromData(const std::vector<uint8_t> &data, bool is_zx81) {
+	std::wstring string;
+
+	wchar_t zx80_map[64] = {
+		' ',	u'\u2598',	u'\u259d',	u'\u2580',	u'\u2596',	u'\u258c',	u'\u259e',	u'\u259b',	u'\u2588',	u'\u2584',	u'\u2580',	'"',	u'£',	'$',	':',	'?',
+		'(',	')',		'>',		'<',		'=',		'+',		'-',		'*',		'/',		';',		',',		'.',	'0',	'1',	'2',	'3',
+		'4',	'5',		'6',		'7',		'8',		'9',		'A',		'B',		'C',		'D',		'E',		'F',	'G',	'H',	'I',	'J',
+		'K',	'L',		'M',		'N',		'O',		'P',		'Q',		'R',		'S',		'T',		'U',		'V',	'W',	'X',	'Y',	'Z'
+	};
+	// TODO: the block character conversions shown here are in the wrong order
+	wchar_t zx81_map[64] = {
+		' ',	u'\u2598',	u'\u259d',	u'\u2580',	u'\u2596',	u'\u258c',	u'\u259e',	u'\u259b',	u'\u2588',	u'\u2584',	u'\u2580',	'"',	u'£',	'$',	':',	'?',
+		'(',	')',		'-',		'+',		'*',		'/',		'=',		'>',		'<',		';',		',',		'.',	'0',	'1',	'2',	'3',
+		'4',	'5',		'6',		'7',		'8',		'9',		'A',		'B',		'C',		'D',		'E',		'F',	'G',	'H',	'I',	'J',
+		'K',	'L',		'M',		'N',		'O',		'P',		'Q',		'R',		'S',		'T',		'U',		'V',	'W',	'X',	'Y',	'Z'
+	};
+	wchar_t *map = is_zx81 ? zx81_map : zx80_map;
+
+	for(uint8_t byte : data) {
+		string.push_back(map[byte & 0x3f]);
+	}
+
+	return string;
+}
+
+std::vector<uint8_t> DataFromString(const std::wstring &string, bool is_zx81) {
+	std::vector<uint8_t> data;
+
+	// TODO
+
+	return data;
+}
--- a/Storage/Data/ZX8081.hpp
+++ b/Storage/Data/ZX8081.hpp
@ -0,0 +1,36 @@
+//
+//  ZX8081.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 08/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#ifndef Storage_Data_ZX8081_hpp
+#define Storage_Data_ZX8081_hpp
+
+#include <string>
+#include <vector>
+#include <cstdint>
+
+namespace Storage {
+namespace Data {
+namespace ZX8081 {
+
+struct File {
+	std::vector<uint8_t> data;
+	std::string name;
+	bool isZX81;
+};
+
+std::shared_ptr<File> FileFromData(const std::vector<uint8_t> &data);
+
+std::wstring StringFromData(const std::vector<uint8_t> &data, bool is_zx81);
+std::vector<uint8_t> DataFromString(const std::wstring &string, bool is_zx81);
+
+
+}
+}
+}
+
+#endif /* ZX8081_hpp */
--- a/Storage/Tape/Formats/ZX80O81P.cpp
+++ b/Storage/Tape/Formats/ZX80O81P.cpp
@ -0,0 +1,102 @@
+//
+//  ZX80O.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 04/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#include "ZX80O81P.hpp"
+#include "../../Data/ZX8081.hpp"
+
+using namespace Storage::Tape;
+
+ZX80O81P::ZX80O81P(const char *file_name) :
+	Storage::FileHolder(file_name) {
+
+	// Grab the actual file contents
+	data_.resize((size_t)file_stats_.st_size);
+	fread(data_.data(), 1, (size_t)file_stats_.st_size, file_);
+
+	// If it's a ZX81 file, prepend a file name.
+	char type = (char)tolower(file_name[strlen(file_name) - 1]);
+	if(type == 'p' || type == '1') {
+		// TODO, maybe: prefix a proper file name; this is leaving the file nameless.
+		data_.insert(data_.begin(), 0x80);
+	}
+
+	std::shared_ptr<::Storage::Data::ZX8081::File> file = Storage::Data::ZX8081::FileFromData(data_);
+	if(!file) throw ErrorNotZX80O81P;
+
+	// then rewind and start again
+	virtual_reset();
+}
+
+void ZX80O81P::virtual_reset() {
+	data_pointer_ = 0;
+	is_past_silence_ = false;
+	has_ended_final_byte_ = false;
+	is_high_ = true;
+	bit_pointer_ = wave_pointer_ = 0;
+}
+
+bool ZX80O81P::has_finished_data() {
+	return (data_pointer_ == data_.size()) && !wave_pointer_ && !bit_pointer_;
+}
+
+bool ZX80O81P::is_at_end() {
+	return has_finished_data() && has_ended_final_byte_;
+}
+
+Tape::Pulse ZX80O81P::virtual_get_next_pulse() {
+	Tape::Pulse pulse;
+
+	// Start with 1 second of silence.
+	if(!is_past_silence_ || has_finished_data()) {
+		pulse.type = Pulse::Type::Low;
+		pulse.length.length = 5;
+		pulse.length.clock_rate = 1;
+		is_past_silence_ = true;
+		has_ended_final_byte_ = has_finished_data();
+		return pulse;
+	}
+
+	// For each byte, output 8 bits and then silence.
+	if(!bit_pointer_ && !wave_pointer_) {
+		byte_ = data_[data_pointer_];
+		data_pointer_++;
+		bit_pointer_ = 0;
+		wave_pointer_ = 0;
+	}
+
+	if(!wave_pointer_) {
+		// post-waves silence (here actually a pre-waves silence) is 1300µs
+		pulse.length.length = 13;
+		pulse.length.clock_rate = 10000;
+		pulse.type = Pulse::Type::Low;
+
+		wave_pointer_ ++;
+	} else {
+		// pulses are of length 150µs
+		pulse.length.length = 3;
+		pulse.length.clock_rate = 20000;
+
+		if(is_high_) {
+			pulse.type = Pulse::Type::High;
+			is_high_ = false;
+		} else {
+			pulse.type = Pulse::Type::Low;
+			is_high_ = true;
+
+			// Bytes are stored MSB first.
+			int wave_count = (byte_ & (0x80 >> bit_pointer_)) ? 9 : 4;
+			wave_pointer_++;
+			if(wave_pointer_ == wave_count + 1) {
+				bit_pointer_ = (bit_pointer_ + 1)&7;
+				wave_pointer_ = 0;
+			}
+		}
+	}
+
+	return pulse;
+}
--- a/Storage/Tape/Formats/ZX80O81P.hpp
+++ b/Storage/Tape/Formats/ZX80O81P.hpp
@ -0,0 +1,58 @@
+//
+//  ZX80O.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 04/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#ifndef ZX80O81P_hpp
+#define ZX80O81P_hpp
+
+#include "../Tape.hpp"
+#include "../../FileHolder.hpp"
+
+#include <cstdint>
+#include <vector>
+
+namespace Storage {
+namespace Tape {
+
+/*!
+	Provides a @c Tape containing a ZX80-format .O tape image, which is a byte stream capture.
+*/
+class ZX80O81P: public Tape, public Storage::FileHolder {
+	public:
+		/*!
+			Constructs an @c ZX80O containing content from the file with name @c file_name.
+
+			@throws ErrorNotZX80O if this file could not be opened and recognised as a valid ZX80-format .O.
+		*/
+		ZX80O81P(const char *file_name);
+
+		enum {
+			ErrorNotZX80O81P
+		};
+
+		// implemented to satisfy @c Tape
+		bool is_at_end();
+
+	private:
+		void virtual_reset();
+		Pulse virtual_get_next_pulse();
+		bool has_finished_data();
+
+		uint8_t byte_;
+		int bit_pointer_;
+		int wave_pointer_;
+		bool is_past_silence_, has_ended_final_byte_;
+		bool is_high_;
+
+		std::vector<uint8_t> data_;
+		size_t data_pointer_;
+};
+
+}
+}
+
+#endif /* ZX80O_hpp */
--- a/Storage/Tape/Parsers/TapeParser.hpp
+++ b/Storage/Tape/Parsers/TapeParser.hpp
@ -13,6 +13,7 @@

 #include <memory>
 #include <vector>
+#include <assert.h>

 namespace Storage {
 namespace Tape {
@ -27,33 +28,50 @@ namespace Tape {
 template <typename WaveType, typename SymbolType> class Parser {
 	public:
 		/// Instantiates a new parser with the supplied @c tape.
-		Parser() : _has_next_symbol(false), _error_flag(false) {}
+		Parser() : has_next_symbol_(false), error_flag_(false) {}

 		/// Resets the error flag.
-		void reset_error_flag()		{	_error_flag = false;		}
+		void reset_error_flag()		{	error_flag_ = false;		}
 		/// @returns @c true if an error has occurred since the error flag was last reset; @c false otherwise.
-		bool get_error_flag()		{	return _error_flag;			}
+		bool get_error_flag()		{	return error_flag_;			}

 		/*!
 			Asks the parser to continue taking pulses from the tape until either the subclass next declares a symbol
 			or the tape runs out, returning the most-recently declared symbol.
 		*/
-		SymbolType get_next_symbol(const std::shared_ptr<Storage::Tape::Tape> &tape)
-		{
-			while(!_has_next_symbol && !tape->is_at_end())
-			{
+		SymbolType get_next_symbol(const std::shared_ptr<Storage::Tape::Tape> &tape) {
+			while(!has_next_symbol_ && !tape->is_at_end()) {
 				process_pulse(tape->get_next_pulse());
 			}
-			_has_next_symbol = false;
-			return _next_symbol;
+			if(tape->is_at_end()) mark_end();
+			has_next_symbol_ = false;
+			return next_symbol_;
 		}

+		/*!
+			This class provides a single token of lookahead; return_symbol allows the single previous
+			token supplied by get_next_symbol to be returned, in which case it will be the thing returned
+			by the next call to get_next_symbol.
+		*/
+		void return_symbol(SymbolType symbol) {
+			assert(!has_next_symbol_);
+			has_next_symbol_ = true;
+			next_symbol_ = symbol;
+		}
+
+
 		/*!
 			Should be implemented by subclasses. Consumes @c pulse. Is likely either to call @c push_wave
 			or to take no action.
 		*/
 		virtual void process_pulse(Storage::Tape::Tape::Pulse pulse) = 0;

+		/*!
+			An optional implementation for subclasses; called to announce that the tape has ended: that
+			no more process_pulse calls will occur.
+		*/
+		virtual void mark_end() {}
+
 	protected:

 		/*!
@ -61,10 +79,9 @@ template <typename WaveType, typename SymbolType> class Parser {
 			
 			Expected to be called by subclasses from @c process_pulse as and when recognised waves arise.
 		*/
-		void push_wave(WaveType wave)
-		{
-			_wave_queue.push_back(wave);
-			inspect_waves(_wave_queue);
+		void push_wave(WaveType wave) {
+			wave_queue_.push_back(wave);
+			inspect_waves(wave_queue_);
 		}

 		/*!
@ -73,9 +90,8 @@ template <typename WaveType, typename SymbolType> class Parser {
 			Expected to be called by subclasses from @c process_pulse if it is recognised that the first set of waves
 			do not form a valid symbol.
 		*/
-		void remove_waves(int number_of_waves)
-		{
-			_wave_queue.erase(_wave_queue.begin(), _wave_queue.begin()+number_of_waves);
+		void remove_waves(int number_of_waves) {
+			wave_queue_.erase(wave_queue_.begin(), wave_queue_.begin()+number_of_waves);
 		}

 		/*!
@ -84,20 +100,25 @@ template <typename WaveType, typename SymbolType> class Parser {
 			Expected to be called by subclasses from @c process_pulse when it recognises that the first @c number_of_waves
 			waves together represent @c symbol.
 		*/
-		void push_symbol(SymbolType symbol, int number_of_waves)
-		{
-			_has_next_symbol = true;
-			_next_symbol = symbol;
+		void push_symbol(SymbolType symbol, int number_of_waves) {
+			has_next_symbol_ = true;
+			next_symbol_ = symbol;
 			remove_waves(number_of_waves);
 		}

-		void set_error_flag()
-		{
-			_error_flag = true;
+		void set_error_flag() {
+			error_flag_ = true;
+		}
+
+		/*!
+			@returns `true` if there is no data left on the tape and the WaveType queue has been exhausted; `false` otherwise.
+		*/
+		bool is_at_end(const std::shared_ptr<Storage::Tape::Tape> &tape) {
+			return tape->is_at_end() && wave_queue_.empty() && !has_next_symbol_;
 		}

 	private:
-		bool _error_flag;
+		bool error_flag_;

 		/*!
 			Should be implemented by subclasses. Inspects @c waves for a potential new symbol. If one is
@ -107,9 +128,9 @@ template <typename WaveType, typename SymbolType> class Parser {
 		*/
 		virtual void inspect_waves(const std::vector<WaveType> &waves) = 0;

-		std::vector<WaveType> _wave_queue;
-		SymbolType _next_symbol;
-		bool _has_next_symbol;
+		std::vector<WaveType> wave_queue_;
+		SymbolType next_symbol_;
+		bool has_next_symbol_;
 };

 }
--- a/Storage/Tape/Parsers/ZX8081.cpp
+++ b/Storage/Tape/Parsers/ZX8081.cpp
@ -0,0 +1,136 @@
+//
+//  ZX8081.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 07/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#include "ZX8081.hpp"
+
+using namespace Storage::Tape::ZX8081;
+
+Parser::Parser() : pulse_was_high_(false), pulse_time_(0) {}
+
+void Parser::process_pulse(Storage::Tape::Tape::Pulse pulse) {
+	pulse_time_ += pulse.length;
+	bool pulse_is_high = pulse.type == Storage::Tape::Tape::Pulse::High;
+
+	if(pulse_is_high == pulse_was_high_) return;
+	pulse_was_high_ = pulse_is_high;
+	post_pulse();
+}
+
+void Parser::post_pulse() {
+	const float expected_pulse_length = 150.0f / 1000000.0f;
+	const float expected_gap_length = 1300.0f / 1000000.0f;
+	float pulse_time = pulse_time_.get_float();
+	pulse_time_.set_zero();
+
+	if(pulse_time > expected_gap_length * 1.25f) {
+		push_wave(WaveType::LongGap);
+	}
+	else if(pulse_time > expected_pulse_length * 1.25f) {
+		push_wave(WaveType::Gap);
+	}
+	else if(pulse_time >= expected_pulse_length * 0.75f && pulse_time <= expected_pulse_length * 1.25f) {
+		push_wave(WaveType::Pulse);
+	}
+	else {
+		push_wave(WaveType::Unrecognised);
+	}
+}
+
+void Parser::mark_end() {
+	// Push the last thing detected, and post an 'unrecognised' to ensure
+	// the queue empties out.
+	post_pulse();
+	push_wave(WaveType::Unrecognised);
+}
+
+void Parser::inspect_waves(const std::vector<WaveType> &waves) {
+	// A long gap is a file gap.
+	if(waves[0] == WaveType::LongGap) {
+		push_symbol(SymbolType::FileGap, 1);
+		return;
+	}
+
+	if(waves.size() >= 9) {
+		size_t wave_offset = 0;
+		// If the very first thing is a gap, swallow it.
+		if(waves[0] == WaveType::Gap) {
+			wave_offset = 1;
+		}
+
+		// Count the number of pulses at the start of this vector
+		size_t number_of_pulses = 0;
+		while(waves[number_of_pulses + wave_offset] == WaveType::Pulse && number_of_pulses < waves.size()) {
+			number_of_pulses++;
+		}
+
+		// If those pulses were followed by a gap then they might be
+		// a recognised symbol.
+		if(number_of_pulses > 17 || number_of_pulses < 7) {
+			push_symbol(SymbolType::Unrecognised, 1);
+		}
+		else if(number_of_pulses + wave_offset < waves.size() &&
+			(waves[number_of_pulses + wave_offset] == WaveType::LongGap || waves[number_of_pulses + wave_offset] == WaveType::Gap)) {
+			// A 1 is 18 up/down waves, a 0 is 8. But the final down will be indistinguishable from
+			// the gap that follows the bit due to the simplified "high is high, everything else is low"
+			// logic applied to pulse detection. So those two things will merge. Meaning we're looking for
+			// 17 and/or 7 pulses.
+			int gaps_to_swallow = (int)wave_offset + ((waves[number_of_pulses + wave_offset] == WaveType::Gap) ? 1 : 0);
+			switch(number_of_pulses) {
+				case 17:	push_symbol(SymbolType::One, 17 + gaps_to_swallow);	break;
+				case 7:		push_symbol(SymbolType::Zero, 7 + gaps_to_swallow);	break;
+				default:	push_symbol(SymbolType::Unrecognised, 1);			break;
+			}
+		}
+	}
+}
+
+int Parser::get_next_byte(const std::shared_ptr<Storage::Tape::Tape> &tape) {
+	int c = 8;
+	int result = 0;
+	while(c--) {
+		if(is_at_end(tape)) return -1;
+		SymbolType symbol = get_next_symbol(tape);
+		if(symbol == SymbolType::FileGap) {
+			return_symbol(symbol);
+			return -1;
+		}
+		if(symbol != SymbolType::One && symbol != SymbolType::Zero) {
+			return -1;
+		}
+		result = (result << 1) | (symbol == SymbolType::One ? 1 : 0);
+	}
+	return result;
+}
+
+std::shared_ptr<std::vector<uint8_t>> Parser::get_next_file_data(const std::shared_ptr<Storage::Tape::Tape> &tape) {
+	if(is_at_end(tape)) return nullptr;
+	SymbolType symbol = get_next_symbol(tape);
+	if(symbol != SymbolType::FileGap) {
+		return nullptr;
+	}
+	while(symbol == SymbolType::FileGap && !is_at_end(tape)) {
+		symbol = get_next_symbol(tape);
+	}
+	if(is_at_end(tape)) return nullptr;
+	return_symbol(symbol);
+
+	std::shared_ptr<std::vector<uint8_t>> result(new std::vector<uint8_t>);
+	int byte;
+	while(!is_at_end(tape)) {
+		byte = get_next_byte(tape);
+		if(byte == -1) return result;
+		result->push_back((uint8_t)byte);
+	}
+	return result;
+}
+
+std::shared_ptr<Storage::Data::ZX8081::File> Parser::get_next_file(const std::shared_ptr<Storage::Tape::Tape> &tape) {
+	std::shared_ptr<std::vector<uint8_t>> file_data = get_next_file_data(tape);
+	if(!file_data) return nullptr;
+	return Storage::Data::ZX8081::FileFromData(*file_data);
+}
--- a/Storage/Tape/Parsers/ZX8081.hpp
+++ b/Storage/Tape/Parsers/ZX8081.hpp
@ -0,0 +1,65 @@
+//
+//  ZX8081.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 07/06/2017.
+//  Copyright © 2017 Thomas Harte. All rights reserved.
+//
+
+#ifndef Storage_Tape_Parsers_ZX8081_hpp
+#define Storage_Tape_Parsers_ZX8081_hpp
+
+#include "TapeParser.hpp"
+
+#include "../../Data/ZX8081.hpp"
+
+#include <string>
+#include <vector>
+#include <cstdint>
+
+namespace Storage {
+namespace Tape {
+namespace ZX8081 {
+
+enum class WaveType {
+	Pulse, Gap, LongGap, Unrecognised
+};
+
+enum class SymbolType {
+	One, Zero, FileGap, Unrecognised
+};
+
+class Parser: public Storage::Tape::Parser<WaveType, SymbolType> {
+	public:
+		Parser();
+
+		/*!
+			Reads and combines the next eight bits. Returns -1 if any errors are encountered.
+		*/
+		int get_next_byte(const std::shared_ptr<Storage::Tape::Tape> &tape);
+
+		/*!
+			Waits for a long gap, reads all the bytes between that and the next long gap, then
+			attempts to parse those as a valid ZX80 or ZX81 file. If no file is found,
+			returns nullptr.
+		*/
+		std::shared_ptr<Storage::Data::ZX8081::File> get_next_file(const std::shared_ptr<Storage::Tape::Tape> &tape);
+
+	private:
+		bool pulse_was_high_;
+		Time pulse_time_;
+		void post_pulse();
+
+		void process_pulse(Storage::Tape::Tape::Pulse pulse);
+		void mark_end();
+
+		void inspect_waves(const std::vector<WaveType> &waves);
+
+		std::shared_ptr<std::vector<uint8_t>> get_next_file_data(const std::shared_ptr<Storage::Tape::Tape> &tape);
+};
+
+}
+}
+}
+
+#endif /* ZX8081_hpp */
--- a/Storage/Tape/Tape.cpp
+++ b/Storage/Tape/Tape.cpp
@ -19,22 +19,19 @@ TapePlayer::TapePlayer(unsigned int input_clock_rate) :

 #pragma mark - Seeking

-void Storage::Tape::Tape::seek(Time &seek_time)
-{
+void Storage::Tape::Tape::seek(Time &seek_time) {
 	current_time_.set_zero();
 	next_time_.set_zero();
 	while(next_time_ < seek_time) get_next_pulse();
 }

-void Storage::Tape::Tape::reset()
-{
+void Storage::Tape::Tape::reset() {
 	current_time_.set_zero();
 	next_time_.set_zero();
 	virtual_reset();
 }

-Tape::Pulse Tape::get_next_pulse()
-{
+Tape::Pulse Tape::get_next_pulse() {
 	Tape::Pulse pulse = virtual_get_next_pulse();
 	current_time_ = next_time_;
 	next_time_ += pulse.length;
@ -43,30 +40,25 @@ Tape::Pulse Tape::get_next_pulse()

 #pragma mark - Player

-void TapePlayer::set_tape(std::shared_ptr<Storage::Tape::Tape> tape)
-{
+void TapePlayer::set_tape(std::shared_ptr<Storage::Tape::Tape> tape) {
 	tape_ = tape;
 	reset_timer();
 	get_next_pulse();
 }

-std::shared_ptr<Storage::Tape::Tape> TapePlayer::get_tape()
-{
+std::shared_ptr<Storage::Tape::Tape> TapePlayer::get_tape() {
 	return tape_;
 }

-bool TapePlayer::has_tape()
-{
+bool TapePlayer::has_tape() {
 	return (bool)tape_;
 }

-void TapePlayer::get_next_pulse()
-{
+void TapePlayer::get_next_pulse() {
 	// get the new pulse
 	if(tape_)
 		current_pulse_ = tape_->get_next_pulse();
-	else
-	{
+	else {
 		current_pulse_.length.length = 1;
 		current_pulse_.length.clock_rate = 1;
 		current_pulse_.type = Tape::Pulse::Zero;
@ -75,21 +67,17 @@ void TapePlayer::get_next_pulse()
 	set_next_event_time_interval(current_pulse_.length);
 }

-void TapePlayer::run_for_cycles(int number_of_cycles)
-{
-	if(has_tape())
-	{
+void TapePlayer::run_for_cycles(int number_of_cycles) {
+	if(has_tape()) {
 		TimedEventLoop::run_for_cycles(number_of_cycles);
 	}
 }

-void TapePlayer::run_for_input_pulse()
-{
+void TapePlayer::run_for_input_pulse() {
 	jump_to_next_event();
 }

-void TapePlayer::process_next_event()
-{
+void TapePlayer::process_next_event() {
 	process_input_pulse(current_pulse_);
 	get_next_pulse();
 }
@ -100,38 +88,30 @@ BinaryTapePlayer::BinaryTapePlayer(unsigned int input_clock_rate) :
 	TapePlayer(input_clock_rate), motor_is_running_(false)
 {}

-void BinaryTapePlayer::set_motor_control(bool enabled)
-{
+void BinaryTapePlayer::set_motor_control(bool enabled) {
 	motor_is_running_ = enabled;
 }

-void BinaryTapePlayer::set_tape_output(bool set)
-{
+void BinaryTapePlayer::set_tape_output(bool set) {
 	// TODO
 }

-bool BinaryTapePlayer::get_input()
-{
+bool BinaryTapePlayer::get_input() {
 	return input_level_;
 }

-void BinaryTapePlayer::run_for_cycles(int number_of_cycles)
-{
+void BinaryTapePlayer::run_for_cycles(int number_of_cycles) {
 	if(motor_is_running_) TapePlayer::run_for_cycles(number_of_cycles);
 }

-void BinaryTapePlayer::set_delegate(Delegate *delegate)
-{
+void BinaryTapePlayer::set_delegate(Delegate *delegate) {
 	delegate_ = delegate;
 }

-void BinaryTapePlayer::process_input_pulse(Storage::Tape::Tape::Pulse pulse)
-{
+void BinaryTapePlayer::process_input_pulse(Storage::Tape::Tape::Pulse pulse) {
 	bool new_input_level = pulse.type == Tape::Pulse::Low;
-	if(input_level_ != new_input_level)
-	{
+	if(input_level_ != new_input_level) {
 		input_level_ = new_input_level;
 		if(delegate_) delegate_->tape_did_change_input(this);
 	}
 }
-