Mercurial > repos > blastem
view cdd_mcu.c @ 2069:8e51c0c3f2e3 segacd
Initial attempt at implementing the Sega CD graphics hardware
author | Michael Pavone <pavone@retrodev.com> |
---|---|
date | Sun, 30 Jan 2022 19:55:33 -0800 |
parents | f22e04b69272 |
children | c69e42444f96 |
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#include "cdd_mcu.h" #include "backend.h" #define SCD_MCLKS 50000000 #define CD_BLOCK_CLKS 16934400 #define CDD_MCU_DIVIDER 8 #define SECTOR_CLOCKS (CD_BLOCK_CLKS/75) #define NIBBLE_CLOCKS (CDD_MCU_DIVIDER * 77) #define BYTE_CLOCKS (SECTOR_CLOCKS/2352) // 96 //lead in start max diameter 46 mm //program area start max diameter 50 mm //difference 4 mm = 4000 um //radius difference 2 mm = 2000 um //track pitch 1.6 um //1250 physical tracks in between //linear speed 1.2 m/s - 1.4 m/s // 1.3 m = 1300 mm // circumference at 46 mm ~ 144.51 mm // circumference at 50 mm ~ 157.08 mm // avg is 150.795 // 75 sectors per second // 17.3333 mm "typical" length of a sector // ~8.7 sectors per track in lead-in area #define LEADIN_SECTORS 10875 static uint32_t cd_block_to_mclks(uint32_t cycles) { return ((uint64_t)cycles) * ((uint64_t)SCD_MCLKS) / ((uint64_t)CD_BLOCK_CLKS); } static uint32_t mclks_to_cd_block(uint32_t cycles) { return ((uint64_t)cycles) * ((uint64_t)CD_BLOCK_CLKS) / ((uint64_t)SCD_MCLKS); } void cdd_mcu_init(cdd_mcu *context, system_media *media) { context->next_int_cycle = CYCLE_NEVER; context->last_subcode_cycle = CYCLE_NEVER; context->last_nibble_cycle = CYCLE_NEVER; context->requested_format = SF_NOTREADY; context->media = media; context->current_status_nibble = -1; context->current_cmd_nibble = -1; } enum { GAO_CDD_CTRL, GAO_CDD_STATUS, GAO_CDD_CMD = GAO_CDD_STATUS+5 }; static uint8_t checksum(uint8_t *vbuffer) { uint8_t *buffer = vbuffer; uint8_t sum = 0; for (int i = 0; i < 9; i++) { sum += buffer[i]; } return (~sum) & 0xF; } #define COARSE_SEEK 2200 //made up numbers #define FINE_SEEK 10 static void handle_seek(cdd_mcu *context) { //TODO: more realistic seeking behavior if (context->seeking) { if (context->seek_pba == context->head_pba) { context->seeking = 0; } else if (context->seek_pba > context->head_pba) { if (context->seek_pba - context->head_pba >= COARSE_SEEK) { context->head_pba += COARSE_SEEK; } else if (context->seek_pba - context->head_pba >= FINE_SEEK) { context->head_pba += FINE_SEEK; } else { context->head_pba++; } } else { if (context->head_pba - context->seek_pba >= COARSE_SEEK) { context->head_pba -= COARSE_SEEK; } else if (context->head_pba >= FINE_SEEK) { context->head_pba -= FINE_SEEK; } else { context->head_pba = 0; } } } } static void lba_to_status(cdd_mcu *context, uint32_t lba) { uint32_t seconds = lba / 75; uint32_t frames = lba % 75; uint32_t minutes = seconds / 60; seconds = seconds % 60; context->status_buffer.b.time.min_high = minutes / 10; context->status_buffer.b.time.min_low = minutes % 10; context->status_buffer.b.time.sec_high = seconds / 10; context->status_buffer.b.time.sec_low = seconds % 10; context->status_buffer.b.time.frame_high = frames / 10; context->status_buffer.b.time.frame_low = frames % 10; } static void update_status(cdd_mcu *context) { switch (context->status) { case DS_PLAY: handle_seek(context); if (!context->seeking) { context->head_pba++; uint32_t lba = context->head_pba - LEADIN_SECTORS; for (uint32_t i = 0; i < context->media->num_tracks; i++) { if (lba < context->media->tracks[i].fake_pregap) { context->in_fake_pregap = 1; break; } lba -= context->media->tracks[i].fake_pregap; if (lba < context->media->tracks[i].start_lba) { context->in_fake_pregap = 1; break; } if (lba < context->media->tracks[i].end_lba) { fseek(context->media->f, lba * 2352, SEEK_SET); context->in_fake_pregap = 0; break; } } } break; case DS_PAUSE: handle_seek(context); break; case DS_TOC_READ: handle_seek(context); if (!context->seeking) { context->head_pba++; if (context->media && context->media->type == MEDIA_CDROM && context->media->num_tracks) { if (context->head_pba > 3*context->media->num_tracks + 1) { context->toc_valid = 1; context->seeking = 1; context->seek_pba = LEADIN_SECTORS + context->media->tracks[0].start_lba; context->status = DS_PAUSE; } } else { context->status = DS_NO_DISC; } } break; } if (context->first_cmd_received) { switch (context->requested_format) { case SF_ABSOLUTE: if (context->toc_valid && context->head_pba >= LEADIN_SECTORS) { lba_to_status(context, context->head_pba - LEADIN_SECTORS); context->status_buffer.format = SF_ABSOLUTE; } else { context->status_buffer.format = SF_NOTREADY; } break; case SF_RELATIVE: if (context->toc_valid && context->head_pba >= LEADIN_SECTORS) { uint32_t lba =context->head_pba - LEADIN_SECTORS; for (uint32_t i = 0; i < context->media->num_tracks; i++) { if (lba < context->media->tracks[i].end_lba) { if (context->media->tracks[i].fake_pregap) { if (lba > context->media->tracks[i].fake_pregap) { lba -= context->media->tracks[i].fake_pregap; } else { //relative time counts down to 0 in pregap lba = context->media->tracks[i].fake_pregap - lba; break; } } if (lba < context->media->tracks[i].start_lba) { //relative time counts down to 0 in pregap lba = context->media->tracks[i].start_lba - lba; } else { lba -= context->media->tracks[i].start_lba; } break; } else if (context->media->tracks[i].fake_pregap) { lba -= context->media->tracks[i].fake_pregap; } } lba_to_status(context, lba); context->status_buffer.format = SF_RELATIVE; } else { context->status_buffer.format = SF_NOTREADY; } break; case SF_TRACK: if (context->toc_valid && context->head_pba >= LEADIN_SECTORS) { uint32_t lba =context->head_pba - LEADIN_SECTORS; uint32_t i; for (i = 0; i < context->media->num_tracks; i++) { if (lba < context->media->tracks[i].end_lba) { if (context->media->tracks[i].fake_pregap) { if (lba > context->media->tracks[i].fake_pregap) { lba -= context->media->tracks[i].fake_pregap; } else { //relative time counts down to 0 in pregap lba = context->media->tracks[i].fake_pregap - lba; break; } } if (lba < context->media->tracks[i].start_lba) { //relative time counts down to 0 in pregap lba = context->media->tracks[i].start_lba - lba; } else { lba -= context->media->tracks[i].start_lba; } break; } else if (context->media->tracks[i].fake_pregap) { lba -= context->media->tracks[i].fake_pregap; } } context->status_buffer.b.track.track_high = (i + 1) / 10; context->status_buffer.b.track.track_low = (i + 1) % 10; if (context->media->tracks[i].type == TRACK_DATA) { context->status_buffer.b.track.control = 4; } else { //TODO: pre-emphasis flag //TODO: copy permitted flag context->status_buffer.b.track.control = 0; } context->status_buffer.b.track.adr = 1; context->status_buffer.format = SF_TRACK; } else { context->status_buffer.format = SF_NOTREADY; } break; case SF_TOCO: if (context->toc_valid) { uint32_t total_fake_pregap = 0; for (uint32_t i = 0; i < context->media->num_tracks; i++) { total_fake_pregap += context->media->tracks[i].fake_pregap; } lba_to_status(context, context->media->tracks[context->media->num_tracks - 1].end_lba + total_fake_pregap); context->status_buffer.format = SF_TOCO; } else { context->status_buffer.format = SF_NOTREADY; } break; case SF_TOCT: if (context->toc_valid) { context->status_buffer.b.toct.first_track_high = 0; context->status_buffer.b.toct.first_track_low = 1; context->status_buffer.b.toct.last_track_high = (context->media->num_tracks + 1) / 10; context->status_buffer.b.toct.last_track_low = (context->media->num_tracks + 1) % 10; context->status_buffer.b.toct.version = 0; context->status_buffer.format = SF_TOCT; } else { context->status_buffer.format = SF_NOTREADY; } break; case SF_TOCN: if (context->toc_valid) { uint32_t lba = context->media->tracks[context->requested_track - 1].start_lba; for (uint32_t i = 0; i < context->requested_track; i++) { lba += context->media->tracks[i].fake_pregap; } lba_to_status(context, lba); if (context->media->tracks[context->requested_track - 1].type == TRACK_DATA) { context->status_buffer.b.tocn.frame_low |= 0x80; } context->status_buffer.b.tocn.track_low = context->requested_track % 10; context->status_buffer.format = SF_TOCN; } else { context->status_buffer.format = SF_NOTREADY; } break; case SF_NOTREADY: memset(&context->status_buffer, 0, sizeof(context->status_buffer) - 1); context->status_buffer.format = SF_NOTREADY; break; } if (context->error_status == DS_STOP) { if (context->requested_format >= SF_TOCO && context->requested_format <= SF_TOCN) { context->status_buffer.status = DS_TOC_READ; } else if (context->seeking) { context->status_buffer.status = DS_SEEK; } else { context->status_buffer.status = context->status; } } else { context->status_buffer.status = context->error_status; context->status_buffer.format = SF_NOTREADY; context->error_status = DS_STOP; } if (context->requested_format != SF_TOCN) { context->status_buffer.b.time.flags = 1; //TODO: populate these } } else { // Did not receive our first command so just send zeroes memset(&context->status_buffer, 0, sizeof(context->status_buffer) - 1); } context->status_buffer.checksum = checksum((uint8_t *)&context->status_buffer); if (context->status_buffer.format != SF_NOTREADY) { printf("CDD Status %X%X.%X%X%X%X%X%X.%X%X\n", context->status_buffer.status, context->status_buffer.format, context->status_buffer.b.time.min_high, context->status_buffer.b.time.min_low, context->status_buffer.b.time.sec_high, context->status_buffer.b.time.sec_low, context->status_buffer.b.time.frame_high, context->status_buffer.b.time.frame_low, context->status_buffer.b.time.flags, context->status_buffer.checksum ); } } static void run_command(cdd_mcu *context) { uint8_t check = checksum((uint8_t*)&context->cmd_buffer); printf("cmd %X, checksum: %X, calc: %X\n", context->cmd_buffer.cmd_type, context->cmd_buffer.checksum, check); if (check != context->cmd_buffer.checksum) { context->error_status = DS_SUM_ERROR; return; } if (context->cmd_buffer.must_be_zero) { context->error_status = DS_CMD_ERROR; return; } context->first_cmd_received = 1; switch (context->cmd_buffer.cmd_type) { case CMD_NOP: break; case CMD_STOP: puts("CDD CMD: STOP"); context->status = DS_STOP; context->requested_format = SF_ABSOLUTE; break; case CMD_READ: case CMD_SEEK: { if (context->status == DS_DOOR_OPEN || context->status == DS_TRAY_MOVING || context->status == DS_DISC_LEADOUT || context->status == DS_DISC_LEADIN) { context->error_status = DS_CMD_ERROR; break; } if (context->requested_format == SF_TOCT || context->requested_format == SF_TOCN) { context->requested_format = SF_ABSOLUTE; } if (!context->toc_valid) { context->error_status = DS_CMD_ERROR; break; } uint32_t lba = context->cmd_buffer.b.time.min_high * 10 + context->cmd_buffer.b.time.min_low; lba *= 60; lba += context->cmd_buffer.b.time.sec_high * 10 + context->cmd_buffer.b.time.sec_low; lba *= 75; lba += context->cmd_buffer.b.time.frame_high * 10 + context->cmd_buffer.b.time.frame_low; printf("CDD CMD: %s cmd for lba %d, MM:SS:FF %u%u:%u%u:%u%u\n", context->cmd_buffer.cmd_type == CMD_READ ? "READ" : "SEEK", lba, context->cmd_buffer.b.time.min_high, context->cmd_buffer.b.time.min_low, context->cmd_buffer.b.time.sec_high, context->cmd_buffer.b.time.sec_low, context->cmd_buffer.b.time.frame_high, context->cmd_buffer.b.time.frame_low ); if (lba >= context->media->tracks[0].fake_pregap + context->media->tracks[context->media->num_tracks - 1].end_lba) { context->error_status = DS_CMD_ERROR; break; } context->seek_pba = lba + LEADIN_SECTORS - 4; context->seeking = 1; context->status = context->cmd_buffer.cmd_type == CMD_READ ? DS_PLAY : DS_PAUSE; break; } case CMD_REPORT_REQUEST: switch (context->cmd_buffer.b.format.status_type) { case SF_ABSOLUTE: case SF_RELATIVE: case SF_TRACK: context->requested_format = context->cmd_buffer.b.format.status_type; break; case SF_TOCO: if (context->toc_valid) { context->requested_format = SF_TOCO; } else { context->error_status = DS_CMD_ERROR; context->requested_format = SF_ABSOLUTE; } break; case SF_TOCT: if (context->toc_valid) { if (context->status == DS_STOP) { context->status = DS_TOC_READ; context->seeking = 1; context->seek_pba = 0; } } else { context->status = DS_TOC_READ; context->seeking = 1; context->seek_pba = 0; } context->requested_format = SF_TOCT; break; case SF_TOCN: context->requested_track = context->cmd_buffer.b.format.track_high * 10; context->requested_track += context->cmd_buffer.b.format.track_low; if (!context->media || context->requested_track > context->media->num_tracks) { context->requested_format = SF_ABSOLUTE; context->error_status = DS_CMD_ERROR; } context->status = DS_TOC_READ; context->seeking = 1; context->seek_pba = 0; context->requested_format = SF_TOCN; break; } printf("CDD CMD: REPORT REQUEST(%d), format set to %d\n", context->cmd_buffer.b.format.status_type, context->requested_format); break; case CMD_PAUSE: if (context->status == DS_DOOR_OPEN || context->status == DS_TRAY_MOVING || context->status == DS_DISC_LEADOUT || context->status == DS_DISC_LEADIN) { context->error_status = DS_CMD_ERROR; break; } if (context->requested_format == SF_TOCT || context->requested_format == SF_TOCN) { context->requested_format = SF_ABSOLUTE; } if (!context->toc_valid) { context->error_status = DS_CMD_ERROR; break; } if (context->status == DS_STOP) { context->seeking = 1; context->seek_pba = LEADIN_SECTORS + context->media->tracks[0].fake_pregap + context->media->tracks[0].start_lba; printf("CDD CMD: PAUSE, seeking to %u\n", context->seek_pba); } else { puts("CDD CMD: PAUSE"); } context->status = DS_PAUSE; break; default: printf("CDD CMD: Unimplemented(%d)\n", context->cmd_buffer.cmd_type); } } #define BIT_HOCK 0x4 #define BIT_DRS 0x2 #define BIT_DTS 0x1 void cdd_mcu_run(cdd_mcu *context, uint32_t cycle, uint16_t *gate_array, lc8951* cdc) { uint32_t cd_cycle = mclks_to_cd_block(cycle); if (!(gate_array[GAO_CDD_CTRL] & BIT_HOCK)) { //it's a little unclear if this gates the actual cd block clock or just handshaking //assum it's actually the clock for now context->cycle = cd_cycle; return; } uint32_t next_subcode = context->last_subcode_cycle + SECTOR_CLOCKS; uint32_t next_nibble = context->current_status_nibble >= 0 ? context->last_nibble_cycle + NIBBLE_CLOCKS : CYCLE_NEVER; uint32_t next_cmd_nibble = context->current_cmd_nibble >= 0 ? context->last_nibble_cycle + NIBBLE_CLOCKS : CYCLE_NEVER; uint32_t next_byte = context->current_sector_byte >= 0 ? context->last_byte_cycle + BYTE_CLOCKS : CYCLE_NEVER; for (; context->cycle < cd_cycle; context->cycle += CDD_MCU_DIVIDER) { if (context->cycle >= next_subcode) { context->last_subcode_cycle = context->cycle; next_subcode = context->cycle + SECTOR_CLOCKS; update_status(context); next_nibble = context->cycle; context->current_status_nibble = 0; gate_array[GAO_CDD_STATUS] |= BIT_DRS; if (context->status == DS_PLAY && !context->seeking) { next_byte = context->cycle; context->current_sector_byte = 0; } } if (context->cycle >= next_nibble) { if (context->current_status_nibble == sizeof(cdd_status)) { context->current_status_nibble = -1; gate_array[GAO_CDD_STATUS] &= ~BIT_DRS; if (context->cmd_recv_pending) { context->cmd_recv_pending = 0; context->current_cmd_nibble = 0; gate_array[GAO_CDD_STATUS] |= BIT_DTS; next_nibble = context->cycle + NIBBLE_CLOCKS; } else { context->cmd_recv_wait = 1; next_nibble = CYCLE_NEVER; } } else { uint8_t value = ((uint8_t *)&context->status_buffer)[context->current_status_nibble]; int ga_index = GAO_CDD_STATUS + (context->current_status_nibble >> 1); if (context->current_status_nibble & 1) { gate_array[ga_index] = value | (gate_array[ga_index] & 0xFF00); } else { gate_array[ga_index] = (value << 8) | (gate_array[ga_index] & 0x00FF); } if (context->current_status_nibble == 7) { context->int_pending = 1; context->next_int_cycle = cd_block_to_mclks(cycle + SECTOR_CLOCKS); } context->current_status_nibble++; context->last_nibble_cycle = context->cycle; next_nibble = context->cycle + NIBBLE_CLOCKS; } } else if (context->cycle >= next_cmd_nibble) { if (context->current_cmd_nibble == sizeof(cdd_cmd)) { next_cmd_nibble = CYCLE_NEVER; context->current_cmd_nibble = -1; gate_array[GAO_CDD_STATUS] &= ~BIT_DTS; run_command(context); } else { int ga_index = GAO_CDD_CMD + (context->current_cmd_nibble >> 1); uint8_t value = (context->current_cmd_nibble & 1) ? gate_array[ga_index] : gate_array[ga_index] >> 8; ((uint8_t *)&context->cmd_buffer)[context->current_cmd_nibble] = value; context->current_cmd_nibble++; context->last_nibble_cycle = context->cycle; next_cmd_nibble = context->cycle + NIBBLE_CLOCKS; } } if (context->cycle >= next_byte) { uint8_t byte; if (context->in_fake_pregap) { if (!context->current_sector_byte || (context->current_sector_byte >= 16)) { byte = 0; //TODO: error detection and correction bytes } else if (context->current_sector_byte < 12) { byte = 0xFF; } else if (context->current_sector_byte == 12) { uint32_t minute = ((context->head_pba - LEADIN_SECTORS) / 75) / 60; byte = (minute % 10) | ((minute / 10 ) << 4); } else if (context->current_sector_byte == 13) { uint32_t seconds = ((context->head_pba - LEADIN_SECTORS) / 75) % 60; byte = (seconds % 10) | ((seconds / 10 ) << 4); } else if (context->current_sector_byte == 14) { uint32_t frames = (context->head_pba - LEADIN_SECTORS) % 75; byte = (frames % 10) | ((frames / 10 ) << 4); } else { byte = 1; } } else { byte = fgetc(context->media->f); } lc8951_write_byte(cdc, cd_block_to_mclks(context->cycle), context->current_sector_byte++, byte); context->last_byte_cycle = context->cycle; next_byte = context->cycle + BYTE_CLOCKS; if (context->current_sector_byte == 2352) { context->current_sector_byte = -1; } } } } void cdd_mcu_start_cmd_recv(cdd_mcu *context, uint16_t *gate_array) { if (context->cmd_recv_wait) { context->current_cmd_nibble = 0; gate_array[GAO_CDD_STATUS] |= BIT_DTS; context->last_nibble_cycle = context->cycle; context->cmd_recv_wait = 0; } else { context->cmd_recv_pending = 1; } } void cdd_hock_enabled(cdd_mcu *context) { context->last_subcode_cycle = context->cycle; context->next_int_cycle = cd_block_to_mclks(context->cycle + SECTOR_CLOCKS + 7 * NIBBLE_CLOCKS); } void cdd_hock_disabled(cdd_mcu *context) { context->last_subcode_cycle = CYCLE_NEVER; context->next_int_cycle = CYCLE_NEVER; context->last_nibble_cycle = CYCLE_NEVER; context->current_status_nibble = -1; context->current_cmd_nibble = -1; } void cdd_mcu_adjust_cycle(cdd_mcu *context, uint32_t deduction) { uint32_t cd_deduction = mclks_to_cd_block(deduction); if (context->next_int_cycle != CYCLE_NEVER) { context->next_int_cycle -= deduction; } if (context->last_subcode_cycle != CYCLE_NEVER) { context->last_subcode_cycle -= cd_deduction; } if (context->last_nibble_cycle != CYCLE_NEVER) { context->last_nibble_cycle -= cd_deduction; } if (context->last_byte_cycle != CYCLE_NEVER) { context->last_byte_cycle -= cd_deduction; } }