Started on a real ugly-implementation coroutine approach, and implemented specify as a fairly trivial first command: it has no result phase, and is the only thing called by AMSDOS as part of the initialisation sequence.

Components/8272/i8272.cpp

@@ -12,78 +12,41 @@
 
 using namespace Intel;
 
+namespace {
+const uint8_t StatusRQM = 0x80;	// Set indicates: ready to send or receive from processor.
+}
+
 i8272::i8272(Cycles clock_rate, int clock_rate_multiplier, int revolutions_per_minute) :
-	Storage::Disk::MFMController(clock_rate, clock_rate_multiplier, revolutions_per_minute) {
+	Storage::Disk::MFMController(clock_rate, clock_rate_multiplier, revolutions_per_minute),
+	status_(StatusRQM),
+	interesting_event_mask_((int)Event8272::CommandByte),
+	resume_point_(0),
+	delay_time_(0) {
+	posit_event((int)Event8272::CommandByte);
 }
 
 void i8272::run_for(Cycles cycles) {
 	Storage::Disk::MFMController::run_for(cycles);
+	if(delay_time_ > 0) {
+		if(cycles.as_int() >= delay_time_) {
+			delay_time_ = 0;
+			posit_event((int)Event8272::Timer);
+		} else {
+			delay_time_ -= cycles.as_int();
+		}
+	}
 }
 
 void i8272::set_register(int address, uint8_t value) {
+	// don't consider attempted sets to the status register
 	if(!address) return;
 
-	// TODO: if not accepting commands, return
+	// if not ready for commands, do nothing
+	if(!(status_ & StatusRQM)) return;
 
+	// accumulate latest byte in the command byte sequence
 	command_.push_back(value);
-	size_t necessary_length;
+	posit_event((int)Event8272::CommandByte);
-	switch(command_[0] & 0x1f) {
-		case 0x06:	// read data
-			necessary_length = 9;
-		break;
-		case 0x0b:	// read deleted data
-			necessary_length = 9;
-		break;
-		case 0x05:	// write data
-			necessary_length = 9;
-		break;
-		case 0x09:	// write deleted data
-			necessary_length = 9;
-		break;
-		case 0x02:	// read track
-			necessary_length = 9;
-		break;
-		case 0x0a:	// read ID
-			necessary_length = 2;
-		break;
-		case 0x0d:	// format track
-			necessary_length = 6;
-		break;
-		case 0x11:	// scan low
-			necessary_length = 9;
-		break;
-		case 0x19:	// scan low  or equal
-			necessary_length = 9;
-		break;
-		case 0x1d:	// scan high or equal
-			necessary_length = 9;
-		break;
-		case 0x07:	// recalibrate
-			necessary_length = 2;
-		break;
-		case 0x08:	// sense interrupt status
-			necessary_length = 1;
-		break;
-		case 0x03:	// specify
-			necessary_length = 3;
-		break;
-		case 0x04:	// sense drive status
-			necessary_length = 2;
-		break;
-		case 0x0f:	// seek
-			necessary_length = 3;
-		break;
-		default:	// invalid
-			necessary_length = 1;
-		break;
-	}
-
-	printf("8272 set register %d to %02x\n", address, value);
-
-	if(command_.size() == necessary_length) {
-		printf("8272 Perform!\n");
-		command_.clear();
-	}
 }
 
 uint8_t i8272::get_register(int address) {
@@ -92,9 +55,161 @@ uint8_t i8272::get_register(int address) {
 		return 0xff;
 	} else {
 		printf("8272 get status\n");
-		return 0x80;
+		return status_;
 	}
 }
 
-void i8272::posit_event(Event type) {
+#define BEGIN_SECTION()	switch(resume_point_) { default:
+#define END_SECTION()	}
+
+#define WAIT_FOR_EVENT(mask)	resume_point_ = __LINE__; interesting_event_mask_ = (int)mask; return; case __LINE__:
+
+void i8272::posit_event(int type) {
+	if(!(interesting_event_mask_ & type)) return;
+	interesting_event_mask_ &= ~type;
+
+	BEGIN_SECTION();
+
+	wait_for_command:
+		set_data_mode(Storage::Disk::MFMController::DataMode::Scanning);
+		command_.clear();
+
+	wait_for_complete_command_sequence:
+		status_ |= StatusRQM;
+		WAIT_FOR_EVENT(Event8272::CommandByte)
+		status_ &= ~StatusRQM;
+
+		switch(command_[0] & 0x1f) {
+			case 0x06:	// read data
+				if(command_.size() < 9) goto wait_for_complete_command_sequence;
+				goto read_data;
+
+			case 0x0b:	// read deleted data
+				if(command_.size() < 9) goto wait_for_complete_command_sequence;
+				goto read_deleted_data;
+
+			case 0x05:	// write data
+				if(command_.size() < 9) goto wait_for_complete_command_sequence;
+				goto write_data;
+
+			case 0x09:	// write deleted data
+				if(command_.size() < 9) goto wait_for_complete_command_sequence;
+				goto write_deleted_data;
+
+			case 0x02:	// read track
+				if(command_.size() < 9) goto wait_for_complete_command_sequence;
+				goto read_track;
+
+			case 0x0a:	// read ID
+				if(command_.size() < 2) goto wait_for_complete_command_sequence;
+				goto read_id;
+
+			case 0x0d:	// format track
+				if(command_.size() < 6) goto wait_for_complete_command_sequence;
+				goto format_track;
+
+			case 0x11:	// scan low
+				if(command_.size() < 9) goto wait_for_complete_command_sequence;
+				goto scan_low;
+
+			case 0x19:	// scan low or equal
+				if(command_.size() < 9) goto wait_for_complete_command_sequence;
+				goto scan_low_or_equal;
+
+			case 0x1d:	// scan high or equal
+				if(command_.size() < 9) goto wait_for_complete_command_sequence;
+				goto scan_high_or_equal;
+
+			case 0x07:	// recalibrate
+				if(command_.size() < 2) goto wait_for_complete_command_sequence;
+				goto recalibrate;
+
+			case 0x08:	// sense interrupt status
+				goto sense_interrupt_status;
+
+			case 0x03:	// specify
+				if(command_.size() < 3) goto wait_for_complete_command_sequence;
+				goto specify;
+
+			case 0x04:	// sense drive status
+				if(command_.size() < 2) goto wait_for_complete_command_sequence;
+				goto sense_drive_status;
+
+			case 0x0f:	// seek
+				if(command_.size() < 3) goto wait_for_complete_command_sequence;
+				goto seek;
+
+			default:	// invalid
+				goto invalid;
+		}
+
+	read_data:
+		printf("Read data unimplemented!!");
+		goto wait_for_command;
+
+	read_deleted_data:
+		printf("Read deleted data unimplemented!!");
+		goto wait_for_command;
+
+	write_data:
+		printf("Write data unimplemented!!");
+		goto wait_for_command;
+
+	write_deleted_data:
+		printf("Write deleted data unimplemented!!");
+		goto wait_for_command;
+
+	read_track:
+		printf("Read track unimplemented!!");
+		goto wait_for_command;
+
+	read_id:
+		printf("Read ID unimplemented!!");
+		goto wait_for_command;
+
+	format_track:
+		printf("Fromat track unimplemented!!");
+		goto wait_for_command;
+
+	scan_low:
+		printf("Scan low unimplemented!!");
+		goto wait_for_command;
+
+	scan_low_or_equal:
+		printf("Scan low or equal unimplemented!!");
+		goto wait_for_command;
+
+	scan_high_or_equal:
+		printf("Scan high or equal unimplemented!!");
+		goto wait_for_command;
+
+	recalibrate:
+		printf("Recalibrate unimplemented!!");
+		goto wait_for_command;
+
+	sense_interrupt_status:
+		printf("Sense interrupt status unimplemented!!");
+		goto wait_for_command;
+
+	specify:
+		printf("Specify");
+		step_rate_time_ = command_[1] &0xf0;		// i.e. 16 to 240m
+		head_unload_time_ = command_[1] & 0x0f;		// i.e. 1 to 16ms
+		head_load_time_ = command_[2] & ~1;			// i.e. 2 to 254 ms in increments of 2ms
+		dma_mode_ = !(command_[2] & 1);
+		goto wait_for_command;
+
+	sense_drive_status:
+		printf("Sense drive status unimplemented!!");
+		goto wait_for_command;
+
+	seek:
+		printf("Seek unimplemented!!");
+		goto wait_for_command;
+
+	invalid:
+		// A no-op, causing the FDC to go back into standby mode.
+		goto wait_for_command;
+
+	END_SECTION()
 }

Components/8272/i8272.hpp

@@ -26,9 +26,24 @@ class i8272: public Storage::Disk::MFMController {
 		uint8_t get_register(int address);
 
 	private:
-		void posit_event(Event type);
+		void posit_event(int type);
 		uint8_t status_;
 		std::vector<uint8_t> command_;
+
+		enum class Event8272: int {
+			CommandByte	= (1 << 3),
+			Timer = (1 << 4),
+
+		};
+
+		int interesting_event_mask_;
+		int resume_point_;
+		int delay_time_;
+
+		int step_rate_time_;
+		int head_unload_time_;
+		int head_load_time_;
+		bool dma_mode_;
 };
 
 }