Attempts a complete wiring of 68901 interrupts.

Components/68901/MFP68901.cpp

@@ -50,7 +50,9 @@ uint8_t MFP68901::read(int address) {
 		case 0x0a:
 			LOG("Read: interrupt mask B");
 		return uint8_t(interrupt_mask_);
-		case 0x0b:		LOG("Read: vector");					break;
+		case 0x0b:
+			LOG("Read: vector");
+		return interrupt_vector_;
 		case 0x0c:		LOG("Read: timer A control");			break;
 		case 0x0d:		LOG("Read: timer B control");			break;
 		case 0x0e:		LOG("Read: timers C/D control");		break;
@@ -106,7 +108,10 @@ void MFP68901::write(int address, uint8_t value) {
 			interrupt_mask_ = (interrupt_mask_ & 0xff00) | value;
 			update_interrupts();
 		break;
-		case 0x0b:		LOG("Write: vector " << PADHEX(2) << int(value));					break;
+		case 0x0b:
+			LOG("Write: vector " << PADHEX(2) << int(value));
+			interrupt_vector_ = value;
+		break;
 		case 0x0c:
 		case 0x0d: {
 			const auto timer = address - 0xc;
@@ -261,11 +266,12 @@ void MFP68901::end_interrupts(int interrupt) {
 }
 
 void MFP68901::update_interrupts() {
+	const bool old_interrupt_line = interrupt_line_;
 	interrupt_pending_ = interrupt_in_service_ & interrupt_enable_;
 	interrupt_line_ = interrupt_pending_ & interrupt_mask_;
 
-	if(interrupt_line_) {
-		LOG("Should produce interrupt...");
+	if(interrupt_delegate_ && interrupt_line_ != old_interrupt_line) {
+		interrupt_delegate_->mfp68901_did_change_interrupt_status(this);
 	}
 }
 
@@ -273,7 +279,17 @@ bool MFP68901::get_interrupt_line() {
 	return interrupt_line_;
 }
 
-uint16_t MFP68901::acknowledge_interrupt() {
-	// TODO.
-	return 0;
+uint8_t MFP68901::acknowledge_interrupt() {
+	uint8_t selected_interrupt = 15;
+	uint16_t interrupt_mask = 0x8000;
+	while(!(interrupt_pending_ & interrupt_mask) && interrupt_mask) {
+		interrupt_mask >>= 1;
+		--selected_interrupt;
+	}
+	end_interrupts(interrupt_mask);
+	return (interrupt_vector_ & 0xf0) | selected_interrupt;
+}
+
+void MFP68901::set_interrupt_delegate(InterruptDelegate *delegate) {
+	interrupt_delegate_ = delegate;
 }

Components/68901/MFP68901.hpp

@@ -35,7 +35,12 @@ class MFP68901 {
 		uint8_t get_port_output();
 
 		bool get_interrupt_line();
-		uint16_t acknowledge_interrupt();
+		uint8_t acknowledge_interrupt();
+
+		struct InterruptDelegate {
+			virtual void mfp68901_did_change_interrupt_status(MFP68901 *) = 0;
+		};
+		void set_interrupt_delegate(InterruptDelegate *delegate);
 
 	private:
 		// MARK: - Timers
@@ -69,6 +74,8 @@ class MFP68901 {
 
 		// MARK: - Interrupts
 
+		InterruptDelegate *interrupt_delegate_ = nullptr;
+
 		// Ad hoc documentation: there seems to be a four-stage process here.
 		// This is my current understanding:
 		//
@@ -88,6 +95,7 @@ class MFP68901 {
 		int interrupt_pending_ = 0;
 		int interrupt_mask_ = 0;
 		bool interrupt_line_ = false;
+		uint8_t interrupt_vector_ = 0;
 
 		enum Interrupt {
 			GPIP0				= (1 << 0),

Machines/AtariST/AtariST.cpp

@@ -215,7 +215,8 @@ class ConcreteMachine:
 	public CPU::MC68000::BusHandler,
 	public CRTMachine::Machine,
 	public ClockingHint::Observer,
-	public Motorola::ACIA::ACIA::InterruptDelegate {
+	public Motorola::ACIA::ACIA::InterruptDelegate,
+	public Motorola::MFP68901::MFP68901::InterruptDelegate {
 	public:
 		ConcreteMachine(const Target &target, const ROMMachine::ROMFetcher &rom_fetcher) :
 			mc68000_(*this),
@@ -259,6 +260,8 @@ class ConcreteMachine:
 			keyboard_acia_->set_clocking_hint_observer(this);
 			ikbd_.set_clocking_hint_observer(this);
 
+			mfp_->set_interrupt_delegate(this);
+
 			set_gpip_input();
 		}
 
@@ -290,6 +293,23 @@ class ConcreteMachine:
 
 			/* TODO: DTack, bus error, VPA.  */
 
+			// An interrupt acknowledge, perhaps?
+			if(cycle.operation & Microcycle::InterruptAcknowledge) {
+				// Current implementation: everything other than 6 (i.e. the MFP is autovectored.
+				if((cycle.word_address()&7) != 6) {
+					mc68000_.set_is_peripheral_address(true);
+					return HalfCycles(0);
+				} else {
+					if(cycle.operation & Microcycle::SelectByte) {
+						cycle.value->halves.low = mfp_->acknowledge_interrupt();
+					}
+					return HalfCycles(0);
+				}
+			}
+
+			// Just in case the last cycle was an interrupt acknowledge. TODO: find a better solution?
+			mc68000_.set_is_peripheral_address(false);
+
 			auto address = cycle.word_address();
 //			if(cycle.data_select_active()) printf("%c %06x\n", (cycle.operation & Microcycle::Read) ? 'r' : 'w', *cycle.address & 0xffffff);
 			uint16_t *memory;
@@ -612,6 +632,19 @@ class ConcreteMachine:
 				((keyboard_acia_->get_interrupt_line() || midi_acia_->get_interrupt_line()) ? 0x0 : 0x10)	// Interrupts are active low.
 			);
 		}
+
+		// MARK - MFP input.
+		void mfp68901_did_change_interrupt_status(Motorola::MFP68901::MFP68901 *mfp) final {
+			update_interrupt_input();
+		}
+
+		void update_interrupt_input() {
+			if(mfp_->get_interrupt_line()) {
+				mc68000_.set_interrupt_level(6);
+			} else {
+				mc68000_.set_interrupt_level(0);
+			}
+		}
 };
 
 }