Specs out a new AppleII::Card interface.

Doesn't yet fully implement it on the Apple II side though.

Machines/AppleII/AppleII.cpp

@@ -286,25 +286,29 @@ class ConcreteMachine:
 					break;
 				}
 
-				if(address >= 0xc100 && address < 0xc800) {
+				if(address >= 0xc090 && address < 0xc800) {
+					size_t card_number = 0;
+					AppleII::Card::Select select = AppleII::Card::None;
+
+					if(address >= 0xc100) {
 						/*
 							Decode the area conventionally used by cards for ROMs:
 								0xCn00 to 0xCnff: card n.
 						*/
-					const size_t card_number = (address - 0xc100) >> 8;
-					if(cards_[card_number]) {
-						update_cards();
-						cards_[card_number]->perform_bus_operation(operation, address & 0xff, value);
-					}
-				} else if(address >= 0xc090 && address < 0xc100) {
+						card_number = (address - 0xc100) >> 8;
+						select = AppleII::Card::Device;
+					} else {
 						/*
 							Decode the area conventionally used by cards for registers:
 								C0n0 to C0nF: card n - 8.
 						*/
-					const size_t card_number = (address - 0xc090) >> 4;
+						card_number = (address - 0xc090) >> 4;
+						select = AppleII::Card::IO;
+					}
+
 					if(cards_[card_number]) {
 						update_cards();
-						cards_[card_number]->perform_bus_operation(operation, 0x100 | (address&0xf), value);
+						cards_[card_number]->perform_bus_operation(select, isReadOperation(operation), address, value);
 					}
 				}
 			}

Machines/AppleII/Card.hpp

@@ -15,16 +15,97 @@
 
 namespace AppleII {
 
+/*!
+	This provides a small subset of the interface offered to cards installed in
+	an Apple II, oriented pragmatically around the cards that are implemented.
+
+	The main underlying rule is as it is elsewhere in the emulator: no
+	_inaccurate_ simplifications — no provision of information that shouldn't
+	actually commute, no interfaces that say they do one thing but which by both
+	both sides are coupled through an unwritten understanding of abuse.
+
+	Special notes:
+
+		Devices that announce a select constraint, being interested in acting only
+		when their IO or Device select is active will receive just-in-time @c run_for
+		notifications, as well as being updated at the end of each of the Apple's
+		@c run_for periods, prior to a @c flush.
+
+		Devices that do not announce a select constraint will prima facie receive a
+		@c perform_bus_operation every cycle. They'll also receive a @c flush.
+		It is **highly** recomended that such devices also implement @c Sleeper
+		as they otherwise prima facie require a virtual method call every
+		single cycle.
+*/
 class Card {
 	public:
-		/*! Advances time by @c cycles, of which @c stretches were stretched. */
+		enum Select: int {
+			None	= 0,		// No select line is active
+			IO		= 1 << 0,	// IO select is active
+			Device	= 1 << 1,	// Device select is active
+		};
+
+		/*!
+			Advances time by @c cycles, of which @c stretches were stretched.
+
+			This is posted only to cards that announced a select constraint. Cards with
+			no constraints, that want to be informed of every machine cycle, will receive
+			a call to perform_bus_operation every cycle and should use that for time keeping.
+		*/
 		virtual void run_for(Cycles half_cycles, int stretches) {}
 
-		/*! Performs a bus operation; the card is implicitly selected. */
-		virtual void perform_bus_operation(CPU::MOS6502::BusOperation operation, uint16_t address, uint8_t *value) = 0;
+		/// Requests a flush of any pending audio or video output.
+		virtual void flush() {}
 
-		/*! Supplies a target for observers. */
+		/*!
+			Performs a bus operation.
+
+			@param select The state of the card's select lines: indicates whether the Apple II
+				thinks this card should respond as though this were an IO access, a Device access,
+				or it thinks that the card shouldn't respond.
+			@param is_read @c true if this is a read cycle; @c false otherwise.
+			@param address The current value of the address bus.
+			@param value A pointer to the value of the data bus, not accounting input from cards.
+				If this is a read cycle, the card is permitted to replace this value with the value
+				output by the card, if any. If this is a write cycle, the card should only read
+				this value.
+		*/
+		virtual void perform_bus_operation(Select select, bool is_read, uint16_t address, uint8_t *value) = 0;
+
+		/*!
+			Returns the type of bus selects this card is actually interested in.
+			As specified, the default is that cards will ask to receive perform_bus_operation
+			only when their select lines are active.
+
+			There's a substantial caveat here: cards that register to receive @c None
+			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() {
+			return select_constraints_;
+		}
+
+		/*! Cards may supply a target for activity observation if desired. */
 		virtual void set_activity_observer(Activity::Observer *observer) {}
+
+		struct Delegate {
+			virtual void card_did_change_select_constraints(Card *card) = 0;
+		};
+		void set_delegate(Delegate *delegate) {
+			delegate_ = delegate;
+		}
+
+	protected:
+		int select_constraints_ = IO | Device;
+		Delegate *delegate_ = nullptr;
+		void set_select_constraints(int constraints) {
+			if(constraints == select_constraints_) return;
+			select_constraints_ = constraints;
+			if(delegate_) delegate_->card_did_change_select_constraints(this);
+		}
 };
 
 }

Machines/AppleII/DiskIICard.cpp

@@ -19,19 +19,23 @@ DiskIICard::DiskIICard(const ROMMachine::ROMFetcher &rom_fetcher, bool is_16_sec
 		});
 	boot_ = std::move(*roms[0]);
 	diskii_.set_state_machine(*roms[1]);
+	set_select_constraints(None);
 }
 
-void DiskIICard::perform_bus_operation(CPU::MOS6502::BusOperation operation, uint16_t address, uint8_t *value) {
-	if(address < 0x100) {
-		if(isReadOperation(operation)) *value = boot_[address];
-	} else {
-		// TODO: data input really shouldn't happen only upon a write.
+void DiskIICard::perform_bus_operation(Select select, bool is_read, uint16_t address, uint8_t *value) {
 	diskii_.set_data_input(*value);
+	switch(select) {
+		default: break;
+		case IO: {
 			const int disk_value = diskii_.read_address(address);
-		if(isReadOperation(operation)) {
+			if(is_read) {
 				if(disk_value != diskii_.DidNotLoad)
 					*value = static_cast<uint8_t>(disk_value);
 			}
+		} break;
+		case Device:
+			if(is_read) *value = boot_[address & 0xff];
+		break;
 	}
 }
 

Machines/AppleII/DiskIICard.hpp

@@ -14,6 +14,7 @@
 
 #include "../../Components/DiskII/DiskII.hpp"
 #include "../../Storage/Disk/Disk.hpp"
+#include "../../ClockReceiver/Sleeper.hpp"
 
 #include <cstdint>
 #include <memory>
@@ -25,8 +26,9 @@ class DiskIICard: public Card {
 	public:
 		DiskIICard(const ROMMachine::ROMFetcher &rom_fetcher, bool is_16_sector);
 
-		void perform_bus_operation(CPU::MOS6502::BusOperation operation, uint16_t address, uint8_t *value) override;
+		void perform_bus_operation(Select select, bool is_read, uint16_t address, uint8_t *value) override;
 		void run_for(Cycles cycles, int stretches) override;
+
 		void set_activity_observer(Activity::Observer *observer) override;
 
 		void set_disk(const std::shared_ptr<Storage::Disk::Disk> &disk, int drive);