Makes first effort to wire up the ADB vertical blank input.

However: looking at the disassembly, I'm not sure it really is wired to INTR. So work to do.

InstructionSets/M50740/Executor.cpp

@@ -62,6 +62,20 @@ void Executor::reset() {
 	set_program_counter(uint16_t(memory_[0x1ffe] | (memory_[0x1fff] << 8)));
 }
 
+void Executor::set_interrupt_line(bool line) {
+	// Super hack: interrupt now, if permitted. Otherwise do nothing.
+	// So this will fail to catch enabling of interrupts while the line
+	// is active, amongst other things.
+	if(interrupt_line_ != line) {
+		interrupt_line_ = line;
+
+		// TODO: verify interrupt connection. Externally, but stubbed off here.
+//		if(!interrupt_disable_ && line) {
+//			perform_interrupt<false>(0x1ff4);
+//		}
+	}
+}
+
 uint8_t Executor::read(uint16_t address) {
 	address &= 0x1fff;
 
@@ -78,7 +92,7 @@ uint8_t Executor::read(uint16_t address) {
 		case 0xd0: case 0xd1: case 0xd2: case 0xd3: case 0xd4: case 0xd5: case 0xd6: case 0xd7:
 		case 0xd8: case 0xd9: case 0xda: case 0xdb: case 0xdc: case 0xdd: case 0xde: case 0xdf:
 			LOG("Unimplemented Port R read from " << PADHEX(4) << address);
-		return 0xff;
+		return 0x00;
 
 		// Ports P0–P3.
 		case 0xe0: case 0xe2:
@@ -199,7 +213,7 @@ uint8_t Executor::flags() {
 		carry_flag_;
 }
 
-template<bool is_brk> inline void Executor::perform_interrupt() {
+template<bool is_brk> inline void Executor::perform_interrupt(uint16_t vector) {
 	// BRK has an unused operand.
 	++program_counter_;
 	push(uint8_t(program_counter_ >> 8));
@@ -456,7 +470,7 @@ template <Operation operation, AddressingMode addressing_mode> void Executor::pe
 
 			case AddressingMode::AbsoluteIndirect:
 				address = next16();
-				address = unsigned(memory_[address] | (memory_[(address + 1) & 0x1fff] << 8));
+				address = unsigned(memory_[address & 0x1fff] | (memory_[(address + 1) & 0x1fff] << 8));
 			break;
 
 			default:
@@ -587,7 +601,7 @@ template <Operation operation> void Executor::perform(uint8_t *operand [[maybe_u
 		} break;
 
 		case Operation::BRK:
-			perform_interrupt<true>();
+			perform_interrupt<true>(0x1ff4);
 			--program_counter_;				// To undo the unavoidable increment
 											// after exiting from here.
 		break;

InstructionSets/M50740/Executor.hpp

@@ -40,7 +40,9 @@ class Executor: public CachingExecutor {
 	public:
 		Executor(PortHandler &);
 		void set_rom(const std::vector<uint8_t> &rom);
+
 		void reset();
+		void set_interrupt_line(bool);
 
 		/*!
 			Runs, in discrete steps, the minimum number of instructions as it takes to complete at least @c cycles.
@@ -150,6 +152,7 @@ class Executor: public CachingExecutor {
 
 		// Interrupt and timer  control.
 		uint8_t interrupt_control_ = 0, timer_control_ = 0;
+		bool interrupt_line_ = false;
 
 		// Access helpers.
 		inline uint8_t read(uint16_t address);
@@ -158,7 +161,7 @@ class Executor: public CachingExecutor {
 		inline uint8_t pull();
 		inline void set_flags(uint8_t);
 		inline uint8_t flags();
-		template<bool is_brk> inline void perform_interrupt();
+		template<bool is_brk> inline void perform_interrupt(uint16_t vector);
 		inline void set_port_output(int port);
 
 		// MARK: - Execution time

Machines/Apple/AppleIIgs/ADB.cpp

@@ -16,6 +16,9 @@
 #include "../../../InstructionSets/M50740/Parser.hpp"
 #include "../../../InstructionSets/Disassembler.hpp"
 
+#define LOG_PREFIX "[ADB GLU] "
+#include "../../../Outputs/Log.hpp"
+
 using namespace Apple::IIgs::ADB;
 
 namespace {
@@ -199,7 +202,10 @@ void GLU::set_port_output(int port, uint8_t value) {
 			}
 		} break;
 		case 3:
-			modifier_state_ = value;
+			if(modifier_state_ != (value & 0x30)) {
+				modifier_state_ = value & 0x30;
+				LOG("Modifier state: " << int(value & 0x30));
+			}
 
 			// Output is inverted respective to input; the microcontroller
 			// sets a value of '1' in order to pull the ADB bus low.
@@ -239,3 +245,7 @@ uint8_t GLU::get_port_input(int port) {
 void GLU::run_ports_for(Cycles cycles) {
 	bus_.run_for(cycles);
 }
+
+void GLU::set_vertical_blank(bool is_blank) {
+	executor_.set_interrupt_line(is_blank);
+}

Machines/Apple/AppleIIgs/ADB.hpp

@@ -44,6 +44,8 @@ class GLU: public InstructionSet::M50740::PortHandler {
 		bool get_command_button() const;
 		bool get_option_button() const;
 
+		void set_vertical_blank(bool);
+
 	private:
 		InstructionSet::M50740::Executor executor_;
 

Machines/Apple/AppleIIgs/AppleIIgs.cpp

@@ -895,6 +895,9 @@ class ConcreteMachine:
 			}
 			if(video_.did_flush()) {
 				update_interrupts();
+
+				const bool is_vertical_blank = video_.last_valid()->get_is_vertical_blank(video_.time_since_flush());
+				adb_glu_->set_vertical_blank(is_vertical_blank);
 			}
 
 			return duration;

Machines/Apple/AppleIIgs/Video.cpp

@@ -193,7 +193,7 @@ Cycles Video::get_next_sequence_point() const {
 
 	constexpr int sequence_point_offset = (blank_ticks + left_border_ticks) * CyclesPerTick;
 
-	// Seed as the distance ot the next row 0.
+	// Seed as the distance to the next row 0.
 	int result = CyclesPerLine + sequence_point_offset - cycles_into_row + (Lines - row - 1)*CyclesPerLine;
 
 	// Replace with the start of the next line, if closer.