3b1emu: src/wd279x.c@d52688dad7fd (annotated)

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src/wd279x.c@d52688dad7fd (annotated)

src/wd279x.c

Sun, 05 Dec 2010 03:55:46 +0000

author: Philip Pemberton <philpem@philpem.me.uk>
date: Sun, 05 Dec 2010 03:55:46 +0000
changeset 48: d52688dad7fd
child 49: 545798274dad
permissions: -rw-r--r--

add preliminary WD2797 FDC emulator

 #include <stdint.h>
 #include <stdbool.h>
 #include "wd279x.h"
 /// WD2797 command constants
 enum {
 	CMD_MASK				= 0xF0,		///< Bit mask to detect command bits
 	CMD_RESTORE				= 0x00,		///< Restore (recalibrate, seek to track 0)
 	CMD_SEEK				= 0x10,		///< Seek to given track
 	CMD_STEP				= 0x20,		///< Step
 	CMD_STEP_TU				= 0x30,		///< Step and update track register
 	CMD_STEPIN				= 0x40,		///< Step In
 	CMD_STEPIN_TU			= 0x50,		///< Step In and update track register
 	CMD_STEPOUT				= 0x60,		///< Step Out
 	CMD_STEPOUT_TU			= 0x70,		///< Step Out and update track register
 	CMD_READ_SECTOR			= 0x80,		///< Read Sector
 	CMD_READ_SECTOR_MULTI	= 0x90,		///< Read Multiple Sectors
 	CMD_WRITE_SECTOR		= 0xA0,		///< Write Sector
 	CMD_WRITE_SECTOR_MULTI	= 0xB0,		///< Write Multiple Sectors
 	CMD_READ_ADDRESS		= 0xC0,		///< Read Address (IDAM contents)
 	CMD_FORCE_INTERRUPT		= 0xD0,		///< Force Interrupt
 	CMD_READ_TRACK			= 0xE0,		///< Read Track
 	CMD_FORMAT_TRACK		= 0xF0		///< Format Track
 };
 /**
  * @brief	Initialise a WD2797 context.
  */
 void wd2797_init(WD279X_CTX *ctx)
 {
 	// track, head and sector unknown
 	ctx->track = 0;
 	ctx->head = 0;
 	ctx->sector = 0;
 	// no IRQ or DRQ, no IRQ callback
 	ctx->irql = false;
 	ctx->irqe = false;
 	// no data available
 	ctx->data_pos = 0;
 	ctx->data_len = 0;
 	// No disc image loaded
 	ctx->disc_image = NULL;
 }
 /**
  * @brief	Read IRQ Rising Edge status. Clears Rising Edge status if it is set.
  * @note	No more IRQs will be sent until the Status Register is read, or a new command is written to the CR.
  */
 bool wd279x_get_irq(WD279X_CTX *ctx)
 {
 	// If an IRQ is pending, clear it and return true, otherwise return false
 	if (ctx->irqe) {
 		ctx->irqe = false;
 		return true;
 	} else {
 		return false;
 	}
 }
 /**
  * @brief	Read DRQ status.
  */
 bool wd279x_get_drq(WD279X_CTX *ctx)
 {
 	return (ctx->data_pos < ctx->data_len);
 }
 /**
  * @brief	Read WD279x register.
  */
 uint8_t wd279x_read_reg(WD279X_CTX *ctx, uint8_t addr)
 {
 	uint8_t temp = 0;
 	switch (addr & 0x03) {
 		case WD279X_REG_STATUS:		// Status register
 			// Read from status register clears IRQ
 			ctx->irql = false;
 			// Get current status flags (set by last command)
 			temp = ctx->status;
 			// DRQ bit
 			if (ctx->cmd_has_drq)
 				temp |= (ctx->data_pos < ctx->data_len) ? 0x02 : 0x00;
 			// FDC is busy if there is still data in the buffer
 			temp |= (ctx->data_pos < ctx->data_len) ? 0x01 : 0x00;	// if data in buffer, then DMA hasn't copied it yet, and we're still busy!
 																		// TODO: also if seek delay / read delay hasn't passed (but that's for later)
 			return temp;
 		case WD279X_REG_TRACK:		// Track register
 			return ctx->track;
 		case WD279X_REG_SECTOR:		// Sector register
 			return ctx->sector;
 		case WD279X_REG_DATA:		// Data register
 			// If there's data in the buffer, return it. Otherwise return 0xFF.
 			if (ctx->data_pos < ctx->data_len) {
 				// return data byte and increment pointer
 				return ctx->data[ctx->data_pos++];
 			} else {
 				return 0xff;
 			}
 		default:
 			// shut up annoying compilers which don't recognise unreachable code when they see it
 			// (here's looking at you, gcc!)
 			return 0xff;
 	}
 }
 /**
  * Write WD279X register
  */
 void wd279x_write_reg(WD279X_CTX *ctx, uint8_t addr, uint8_t val)
 {
 	uint8_t cmd = val & CMD_MASK;
 	size_t lba;
 	bool is_type1 = false;
 	switch (addr) {
 		case WD279X_REG_COMMAND:	// Command register
 			// write to command register clears interrupt request
 			ctx->irql = false;
 			// Is the drive ready?
 			if (ctx->disc_image == NULL) {
 				// No disc image, thus the drive is busy.
 				ctx->status = 0x80;
 				return;
 			}
 			// Handle Type 1 commands
 			switch (cmd) {
 				case CMD_RESTORE:
 					// Restore. Set track to 0 and throw an IRQ.
 					is_type1 = true;
 					ctx->track = 0;
 					break;
 				case CMD_SEEK:
 					// Seek. Seek to the track specced in the Data Register.
 					is_type1 = true;
 					if (ctx->data_reg < ctx->geom_tracks) {
 						ctx->track = ctx->data_reg;
 					} else {
 						// Seek error. :(
 						ctx->status = 0x10;
 					}
 				case CMD_STEP:
 					// TODO! deal with trk0!
 					// Need to keep a copy of the track register; when it hits 0, set the TRK0 flag.
 					is_type1 = true;
 					break;
 				case CMD_STEPIN:
 				case CMD_STEPOUT:
 					// TODO! deal with trk0!
 					// Need to keep a copy of the track register; when it hits 0, set the TRK0 flag.
 					if (cmd == CMD_STEPIN) {
 						ctx->last_step_dir = 1;
 					} else {
 						ctx->last_step_dir = -1;
 					}
 					is_type1 = true;
 					break;
 				case CMD_STEP_TU:
 				case CMD_STEPIN_TU:
 				case CMD_STEPOUT_TU:
 					// if this is a Step In or Step Out cmd, set the step-direction
 					if (cmd == CMD_STEPIN_TU) {
 						ctx->last_step_dir = 1;
 					} else if (cmd == CMD_STEPOUT_TU) {
 						ctx->last_step_dir = -1;
 					}
 					// Seek one step in the last direction used.
 					ctx->track += ctx->last_step_dir;
 					if (ctx->track < 0) ctx->track = 0;
 					if (ctx->track >= ctx->geom_tracks) {
 						// Seek past end of disc... that'll be a Seek Error then.
 						ctx->status = 0x10;
 						ctx->track = ctx->geom_tracks - 1;
 					}
 					is_type1 = true;
 					break;
 				default:
 					break;
 			}
 			if (is_type1) {
 				// Terminate any sector reads or writes
 				ctx->data_len = ctx->data_pos = 0;
 				// No DRQ bit for these commands.
 				ctx->cmd_has_drq = false;
 				// Type1 status byte...
 				ctx->status = 0;
 				// S7 = Not Ready. Command executed, therefore the drive was ready... :)
 				// S6 = Write Protect. TODO: add this
 				// S5 = Head Loaded. For certain emulation-related reasons, the heads are always loaded...
 				ctx->status |= 0x20;
 				// S4 = Seek Error. Not bloody likely if we got down here...!
 				// S3 = CRC Error. Not gonna happen on a disc image!
 				// S2 = Track 0
 				ctx->status |= (ctx->track == 0) ? 0x04 : 0x00;
 				// S1 = Index Pulse. TODO -- need periodics to emulate this
 				// S0 = Busy. We just exec'd the command, thus we're not busy.
 				// 		TODO: Set a timer for seeks, and ONLY clear BUSY when that timer expires. Need periodics for that.
 				// Set IRQ only if IRQL has been cleared (no pending IRQs)
 				ctx->irqe = !ctx->irql;
 				ctx->irql = true;
 				return;
 			}
 			// That's the Type 1 (seek) commands sorted. Now for the others.
 			// If drive isn't ready, then set status B7 and exit
 			if (ctx->disc_image == NULL) {
 				ctx->status = 0x80;
 				return;
 			}
 			// If this is a Write command, check write protect status too
 			// TODO!
 			if (false) {
 				// Write protected disc...
 				if ((cmd == CMD_WRITE_SECTOR) || (cmd == CMD_WRITE_SECTOR_MULTI) || (cmd == CMD_FORMAT_TRACK)) {
 					// Set Write Protect bit and bail.
 					ctx->status = 0x40;
 					// Set IRQ only if IRQL has been cleared (no pending IRQs)
 					ctx->irqe = !ctx->irql;
 					ctx->irql = true;
 					return;
 				}
 			}
 			// Disc is ready to go. Parse the command word.
 			switch (cmd) {
 				case CMD_READ_ADDRESS:
 					// Read Address
 					// reset data pointers
 					ctx->data_pos = ctx->data_len = 0;
 					// load data buffer
 					ctx->data[ctx->data_len++] = ctx->track;
 					ctx->data[ctx->data_len++] = ctx->head;
 					ctx->data[ctx->data_len++] = ctx->sector;
 					switch (ctx->geom_secsz) {
 						case 128:	ctx->data[ctx->data_len++] = 0; break;
 						case 256:	ctx->data[ctx->data_len++] = 1; break;
 						case 512:	ctx->data[ctx->data_len++] = 2; break;
 						case 1024:	ctx->data[ctx->data_len++] = 3; break;
 						default:	ctx->data[ctx->data_len++] = 0xFF; break;	// TODO: deal with invalid values better
 					}
 					ctx->data[ctx->data_len++] = 0;	// TODO: IDAM CRC!
 					ctx->data[ctx->data_len++] = 0;
 					// B6, B5 = 0
 					// B4 = Record Not Found. We're not going to see this... FIXME-not emulated
 					// B3 = CRC Error. Not possible.
 					// B2 = Lost Data. Caused if DRQ isn't serviced in time. FIXME-not emulated
 					// B1 = DRQ. Data request.
 					ctx->status |= (ctx->data_pos < ctx->data_len) ? 0x02 : 0x00;
 					break;
 				case CMD_READ_SECTOR:
 				case CMD_READ_SECTOR_MULTI:
 					// Read Sector or Read Sector Multiple
 					// TODO: multiple is not implemented!
 					if (cmd == CMD_READ_SECTOR_MULTI) printf("WD279X: NOTIMP: read-multi\n");
 					// reset data pointers
 					ctx->data_pos = ctx->data_len = 0;
 					// Calculate the LBA address of the required sector
 					lba = ((((ctx->track * ctx->geom_heads) + ctx->head) * ctx->geom_spt) + ctx->sector - 1) * ctx->geom_secsz;
 					// Read the sector from the file
 					fseek(ctx->disc_image, lba, SEEK_SET);
 					ctx->data_len = fread(ctx->data, 1, ctx->geom_secsz, ctx->disc_image);
 					// TODO: if datalen < secsz, BAIL! (call it a crc error or secnotfound maybe? also log to stderr)
 					// TODO: if we're asked to do a Read Multi, malloc for an entire track, then just read a full track...
 					// B6 = 0
 					// B5 = Record Type -- 1 = deleted, 0 = normal. We can't emulate anything but normal data blocks.
 					// B4 = Record Not Found. We're not going to see this... FIXME-not emulated
 					// B3 = CRC Error. Not possible.
 					// B2 = Lost Data. Caused if DRQ isn't serviced in time. FIXME-not emulated
 					// B1 = DRQ. Data request.
 					ctx->status |= (ctx->data_pos < ctx->data_len) ? 0x02 : 0x00;
 					break;
 				case CMD_READ_TRACK:
 					// Read Track
 					// B6, B5, B4, B3 = 0
 					// B2 = Lost Data. Caused if DRQ isn't serviced in time. FIXME-not emulated
 					// B1 = DRQ. Data request.
 					ctx->status |= (ctx->data_pos < ctx->data_len) ? 0x02 : 0x00;
 					break;
 				case CMD_WRITE_SECTOR:
 				case CMD_WRITE_SECTOR_MULTI:
 					// Write Sector or Write Sector Multiple
 					// reset data pointers
 					ctx->data_pos = ctx->data_len = 0;
 					// TODO: set "write pending" flag, and write LBA, and go from there.
 					// B6 = Write Protect. FIXME -- emulate this!
 					// B5 = 0
 					// B4 = Record Not Found. We're not going to see this... FIXME-not emulated
 					// B3 = CRC Error. Not possible.
 					// B2 = Lost Data. Caused if DRQ isn't serviced in time. FIXME-not emulated
 					// B1 = DRQ. Data request.
 					ctx->status |= (ctx->data_pos < ctx->data_len) ? 0x02 : 0x00;
 					break;
 				case CMD_FORMAT_TRACK:
 					// Write Track (aka Format Track)
 					// B6 = Write Protect. FIXME -- emulate this!
 					// B5, B4, B3 = 0
 					// B2 = Lost Data. Caused if DRQ isn't serviced in time. FIXME-not emulated
 					// B1 = DRQ. Data request.
 					ctx->status |= (ctx->data_pos < ctx->data_len) ? 0x02 : 0x00;
 					break;
 				case CMD_FORCE_INTERRUPT:
 					// Force Interrupt...
 					// TODO: terminate current R/W op
 					// TODO: variants for this command
 					break;
 			}
 			break;
 		case WD279X_REG_TRACK:		// Track register
 			ctx->track = val;
 			break;
 		case WD279X_REG_SECTOR:		// Sector register
 			ctx->sector = val;
 			break;
 		case WD279X_REG_DATA:		// Data register
 			// Save the value written into the data register
 			ctx->data_reg = val;
 			// If we're processing a write command, and there's space in the
 			// buffer, allow the write.
 			if (ctx->data_pos < ctx->data_len) {
 				// store data byte and increment pointer
 				ctx->data[ctx->data_pos++] = val;
 			}
 			break;
 	}
 }

3b1emu / annotate

src/wd279x.c@d52688dad7fd (annotated)

src/wd279x.c