Adds enough logic to advance to an ACIA access error.

Components/68901/MFP68901.cpp

@@ -123,11 +123,7 @@ void MFP68901::run_for(HalfCycles time) {
 				--timers_[c].divisor;
 				if(!timers_[c].divisor) {
 					timers_[c].divisor = timers_[c].prescale;
-
+					decrement_timer(c);
-					--timers_[c].value;
-					if(!timers_[c].value) {
-						// TODO: interrupt.
-					}
 				}
 			}
 		}
@@ -159,3 +155,19 @@ void MFP68901::set_timer_data(int timer, uint8_t value) {
 uint8_t MFP68901::get_timer_data(int timer) {
 	return timers_[timer].value;
 }
+
+void MFP68901::set_timer_event_input(int channel, bool value) {
+	if(timers_[channel].event_input == value) return;
+
+	timers_[channel].event_input = value;
+	if(timers_[channel].mode == TimerMode::EventCount && !value) {	/* TODO: which edge is counted? "as defined by the associated Interrupt Channel’s edge bit"?  */
+		decrement_timer(channel);
+	}
+}
+
+void MFP68901::decrement_timer(int timer) {
+	--timers_[timer].value;
+	if(!timers_[timer].value) {
+		// TODO: interrupt. Reload, possibly.
+	}
+}

Components/68901/MFP68901.hpp

@@ -23,6 +23,8 @@ class MFP68901 {
 		void run_for(HalfCycles);
 		HalfCycles get_next_sequence_point();
 
+		void set_timer_event_input(int channel, bool value);
+
 	private:
 		// MARK: - Timers
 		enum class TimerMode {
@@ -31,6 +33,7 @@ class MFP68901 {
 		void set_timer_mode(int timer, TimerMode, int prescale, bool reset_timer);
 		void set_timer_data(int timer, uint8_t);
 		uint8_t get_timer_data(int timer);
+		void decrement_timer(int timer);
 
 		struct Timer {
 			TimerMode mode = TimerMode::Stopped;
@@ -38,6 +41,7 @@ class MFP68901 {
 			uint8_t reload_value = 0;
 			int prescale = 1;
 			int divisor = 0;
+			bool event_input = false;
 		} timers_[4];
 
 		HalfCycles cycles_left_;

Machines/AtariST/AtariST.cpp

@@ -115,6 +115,8 @@ class ConcreteMachine:
 					address %= rom_.size();
 				break;
 
+				case BusDevice::Unassigned:
+					// TODO: figure out the rules about bus errors.
 				case BusDevice::Cartridge:
 					/*
 						TOS 1.0 appears to attempt to read from the catridge before it has setup
@@ -131,10 +133,6 @@ class ConcreteMachine:
 					}
 				return HalfCycles(0);
 
-				case BusDevice::Unassigned:
-				assert(false);
-				return HalfCycles(0);
-
 				case BusDevice::IO:
 					switch(address) {
 						default:
@@ -236,6 +234,39 @@ class ConcreteMachine:
 									GPIP 0: centronics busy
 							*/
 						break;
+
+						// Video controls.
+						case 0x7fc100:	case 0x7fc101:	case 0x7fc102:	case 0x7fc103:
+						case 0x7fc104:	case 0x7fc105:	case 0x7fc106:	case 0x7fc107:
+						case 0x7fc108:	case 0x7fc109:	case 0x7fc10a:	case 0x7fc10b:
+						case 0x7fc10c:	case 0x7fc10d:	case 0x7fc10e:	case 0x7fc10f:
+						case 0x7fc110:	case 0x7fc111:	case 0x7fc112:	case 0x7fc113:
+						case 0x7fc114:	case 0x7fc115:	case 0x7fc116:	case 0x7fc117:
+						case 0x7fc118:	case 0x7fc119:	case 0x7fc11a:	case 0x7fc11b:
+						case 0x7fc11c:	case 0x7fc11d:	case 0x7fc11e:	case 0x7fc11f:
+						case 0x7fc120:	case 0x7fc121:	case 0x7fc122:	case 0x7fc123:
+						case 0x7fc124:	case 0x7fc125:	case 0x7fc126:	case 0x7fc127:
+						case 0x7fc128:	case 0x7fc129:	case 0x7fc12a:	case 0x7fc12b:
+						case 0x7fc12c:	case 0x7fc12d:	case 0x7fc12e:	case 0x7fc12f:
+						case 0x7fc130:	case 0x7fc131:
+							if(!cycle.data_select_active()) return HalfCycles(0);
+
+							if(cycle.operation & Microcycle::Read) {
+								const uint8_t value = video_->read(int(address));
+								if(cycle.operation & Microcycle::SelectByte) {
+									cycle.value->halves.low = value;
+								} else {
+									cycle.value->halves.high = value;
+									cycle.value->halves.low = 0xff;
+								}
+							} else {
+								if(cycle.operation & Microcycle::SelectByte) {
+									video_->write(int(address), cycle.value->halves.low);
+								} else {
+									video_->write(int(address), cycle.value->halves.high);
+								}
+							}
+						break;
 					}
 				return HalfCycles(0);
 			}
@@ -281,6 +312,8 @@ class ConcreteMachine:
 				cycles_until_video_event_ = video_->get_next_sequence_point();
 
 				// TODO: push v/hsync/display_enable elsewhere.
+				mfp_->set_timer_event_input(1, video_->display_enabled());
+//				printf("%c%c%c\n", video_->display_enabled() ? 'e' : '-', video_->hsync() ? 'h' : '-', video_->vsync() ? 'v' : '-');
 			}
 			cycles_until_video_event_ -= length;
 			video_ += length;

Machines/AtariST/Video.cpp

@@ -8,6 +8,8 @@
 
 #include "Video.hpp"
 
+#include "../../Outputs/Log.hpp"
+
 #include <algorithm>
 
 using namespace Atari::ST;
@@ -66,6 +68,9 @@ void Video::run_for(HalfCycles duration) {
 		x = target;	\
 	}
 
+	// TODO: the below is **way off**. The real hardware does what you'd expect with ongoing state and
+	// exact equality tests. Fixes to come.
+
 	while(integer_duration) {
 		const int final_x = std::min(x + integer_duration, mode_params.line_length);
 		integer_duration -= (final_x - x);
@@ -117,7 +122,7 @@ void Video::run_for(HalfCycles duration) {
 
 void Video::output_border(int duration) {
 	uint16_t *colour_pointer = reinterpret_cast<uint16_t *>(crt_.begin_data(1));
-	if(colour_pointer) *colour_pointer = 0x333;
+	if(colour_pointer) *colour_pointer = palette_[0];
 	crt_.output_level(duration);
 }
 
@@ -178,3 +183,26 @@ HalfCycles Video::get_next_sequence_point() {
 		return (cycles_until_vsync < cycles_until_display_enable) ? cycles_until_vsync : cycles_until_display_enable;
 	}
 }
+
+// MARK: - IO dispatch
+
+uint8_t Video::read(int address) {
+	LOG("[Video] read " << (address & 0x3f));
+	return 0xff;
+}
+
+void Video::write(int address, uint8_t value) {
+	LOG("[Video] write " << PADHEX(2) << int(value) << " to " << PADHEX(2) << (address & 0x3f));
+	address &= 0x3f;
+	switch(address) {
+		default: break;
+
+		// Palette.
+		case 0x20:	case 0x21:	case 0x22:	case 0x23:
+		case 0x24:	case 0x25:	case 0x26:	case 0x27:
+		case 0x28:	case 0x29:	case 0x2a:	case 0x2b:
+		case 0x2c:	case 0x2d:	case 0x2e:	case 0x2f:
+			palette_[address - 0x20] = uint16_t((value & 0x777) << 5);
+		break;
+	}
+}

Machines/AtariST/Video.hpp

@@ -39,9 +39,14 @@ class Video {
 		bool vsync();
 		bool display_enabled();
 
+		uint8_t read(int address);
+		void write(int address, uint8_t value);
+
 	private:
 		Outputs::CRT::CRT crt_;
 
+		uint16_t palette_[16];
+
 		int x = 0, y = 0;
 		void output_border(int duration);
 };