Genesis-Plus-GX/source/eeprom.c

#include "shared.h"
#include "rominfo.h"

#define GAME_COUNT 21

typedef struct
{
	char game_id[14];
	uint16 chk;
	T_EEPROM_TYPE type;
} T_GAME_ENTRY;

T_GAME_ENTRY database[GAME_COUNT] = 
{
	/* ACCLAIM mappers */
	/* 24C02 (old mapper) */
	{{"T-081326"   }, 0,      {8,  0xFF,   0xFF,   0x200000, 0x200000, 0x200000, 0, 1, 1}},   /* NBA Jam (UE) */
	{{"T-81033"    }, 0,      {8,  0xFF,   0xFF,   0x200000, 0x200000, 0x200000, 0, 1, 1}},   /* NBA Jam (J) */
	/* 24C02 */
	{{"T-81406"    }, 0,      {8,  0xFF,   0xFF,   0x200001, 0x200001, 0x200000, 0, 0, 0}},   /* NBA Jam TE */
	{{"T-081276"   }, 0,      {8,  0xFF,   0xFF,   0x200001, 0x200001, 0x200000, 0, 0, 0}},   /* NFL Quarterback Club */
	/* 24C16 */
	{{"T-081586"   }, 0,      {8,  0x7FF,  0x7FF,  0x200001, 0x200001, 0x200000, 0, 0, 0}},   /* NFL Quarterback Club '96 */
	/* 24C65 */
	{{"T-81576"    }, 0,      {16, 0x1FFF, 0x1FFF, 0x200001, 0x200001, 0x200000, 0, 0, 0}},   /* College Slam */
	{{"T-81476"    }, 0,      {16, 0x1FFF, 0x1FFF, 0x200001, 0x200001, 0x200000, 0, 0, 0}},   /* Frank Thomas Big Hurt Baseball */
	
	/* EA mapper (24C01 only) */
	{{"T-50396"    }, 0,      {7,  0x7F,   0x7F,   0x200000, 0x200000, 0x200000, 7, 7, 6}},   /* NHLPA Hockey 93 (UE) */
	{{"T-50176"    }, 0,      {7,  0x7F,   0x7F,   0x200000, 0x200000, 0x200000, 7, 7, 6}},   /* Rings of Power */
	
	/* SEGA mapper (24C01 only) */
	{{"T-12046"    }, 0,      {7,  0x7F,   0x7F,   0x200001, 0x200001, 0x200001, 0, 0, 1}},   /* Megaman - The Wily Wars */
	{{"T-12053"    }, 0xEA80, {7,  0x7F,   0x7F,   0x200001, 0x200001, 0x200001, 0, 0, 1}},   /* Rockman Mega World (J) [A] */
	{{"MK-1215"    }, 0,      {7,  0x7F,   0x7F,   0x200001, 0x200001, 0x200001, 0, 0, 1}},   /* Evander 'Real Deal' Holyfield's Boxing */
	{{"MK-1228"    }, 0,      {7,  0x7F,   0x7F,   0x200001, 0x200001, 0x200001, 0, 0, 1}},   /* Greatest Heavyweights of the Ring (U) */
	{{"G-5538"     }, 0,      {7,  0x7F,   0x7F,   0x200001, 0x200001, 0x200001, 0, 0, 1}},   /* Greatest Heavyweights of the Ring (J) */
	{{"PR-1993"    }, 0,      {7,  0x7F,   0x7F,   0x200001, 0x200001, 0x200001, 0, 0, 1}},   /* Greatest Heavyweights of the Ring (E) */
	{{"G-4060"     }, 0,      {7,  0x7F,   0x7F,   0x200001, 0x200001, 0x200001, 0, 0, 1}},   /* Wonderboy in Monster World */
	
	/* CODEMASTERS mapper */
	/* 24C08 */
	{{"T-120096"   }, 0,      {8,  0x3FF,  0x3FF,  0x300000, 0x380001, 0x300000, 0, 7, 1}},   /* Micro Machines 2 - Turbo Tournament (E) */
	{{"00000000-00"}, 0x168B, {8,  0x3FF,  0x3FF,  0x300000, 0x380001, 0x300000, 0, 7, 1}},   /* Micro Machines Military */
	{{"00000000-00"}, 0xCEE0, {8,  0x3FF,  0x3FF,  0x300000, 0x380001, 0x300000, 0, 7, 1}},   /* Micro Machines Military (Bad)*/
	/* 24C16 */
	{{"00000000-00"}, 0x165E, {8,  0x7FF,  0x7FF,  0x300000, 0x380001, 0x300000, 0, 7, 1}},   /* Micro Machines Turbo Tournament 96 */
	{{"00000000-00"}, 0x2C41, {8,  0x7FF,  0x7FF,  0x300000, 0x380001, 0x300000, 0, 7, 1}}    /* Micro Machines Turbo Tournament 96 (Bad)*/
};


T_EEPROM eeprom;

void EEPROM_Init()
{
	uint8 i = 0;
	
	/* initialize eeprom */
    memset(&eeprom, 0, sizeof(T_EEPROM));
    eeprom.sda = eeprom.old_sda = 1;
	eeprom.scl = eeprom.old_scl	= 1;
	eeprom.state = STAND_BY;

	sram.custom = 0;
  
	/* look into game database */
	while ((i<GAME_COUNT) && (!sram.custom))
	{
		if (strstr(rominfo.product,database[i].game_id) != NULL)
		{
			/* additional check (Micro Machines, Rockman Mega World) */
			if ((database[i].chk == 0) || (database[i].chk == rominfo.checksum))
			{
				sram.custom = 1;
				sram.on = 1;
				sram.write = 1;
				memcpy(&eeprom.type, &database[i].type, sizeof(T_EEPROM_TYPE));

				/* Micromachines II need initialized values in RAM */
				if (i == 16)
				{
					int j=0;
					while (j<0x400)
					{
						/* memory array is filled with "PETETEST01234567" */
						sram.sram[j++] = 0x50;
						sram.sram[j++] = 0x45;
						sram.sram[j++] = 0x54;
						sram.sram[j++] = 0x45;
						sram.sram[j++] = 0x54;
						sram.sram[j++] = 0x45;
						sram.sram[j++] = 0x53;
						sram.sram[j++] = 0x54;
						sram.sram[j++] = 0x30;
						sram.sram[j++] = 0x31;
						sram.sram[j++] = 0x32;
						sram.sram[j++] = 0x33;
						sram.sram[j++] = 0x34;
						sram.sram[j++] = 0x35;
						sram.sram[j++] = 0x36;
						sram.sram[j++] = 0x37;
					}
				}
			}
		}
		i++;
	}

	if (sram.custom)
	{
		/* set SRAM start & end address */
		sram.start = sram.end = eeprom.type.sda_in_adr;
		if (sram.end < eeprom.type.sda_out_adr) sram.end = eeprom.type.sda_out_adr;
		if (sram.end < eeprom.type.scl_adr) sram.end = eeprom.type.scl_adr;
		if (sram.start > eeprom.type.sda_out_adr) sram.start = eeprom.type.sda_out_adr;
		if (sram.start > eeprom.type.scl_adr) sram.start = eeprom.type.scl_adr;
	}
	else if ((sram.end - sram.start) < 2)
	{
		/* Game not found in database but header indicates it uses EEPROM */
		sram.custom = 1;
		sram.on = 1;
		sram.write = 1;
		
		/* set SEGA mapper as default */
		memcpy(&eeprom.type, &database[9].type, sizeof(T_EEPROM_TYPE));
	}
}

static void Detect_START()
{
	if (eeprom.old_scl && eeprom.scl)
	{
		if (eeprom.old_sda && !eeprom.sda)
		{
			eeprom.cycles = 0;
			eeprom.slave_mask = 0;
			if (eeprom.type.address_bits == 7)
			{
				eeprom.word_address = 0;
				eeprom.state = GET_WORD_ADR_7BITS;
			}
			else eeprom.state = GET_SLAVE_ADR;
		}
	}
}

static void Detect_STOP()
{
	if (eeprom.old_scl && eeprom.scl)
	{
		if (!eeprom.old_sda && eeprom.sda)
		{
			eeprom.state = STAND_BY;
		}
	}
}

void EEPROM_Write(unsigned int address, unsigned int value)
{
	uint16 sram_address = 0;

	/* decode SCL and SDA value */
	if (eeprom.type.sda_in_adr == address) eeprom.sda = (value >> eeprom.type.sda_in_bit) & 1;
	else eeprom.sda = eeprom.old_sda;
	if (eeprom.type.scl_adr == address) eeprom.scl = (value >> eeprom.type.scl_bit) & 1;
	else eeprom.scl = eeprom.old_scl;
	
	/* EEPROM current state */
	switch (eeprom.state)
	{
		/* Standby Mode */
		case STAND_BY:
			Detect_START();
			Detect_STOP();
			break;


		/* Suspended Mode */
		case WAIT_STOP:
			Detect_STOP();
			break;


		/* Get Word Address 7 bits: MODE-1 only (24C01)
		 * and R/W bit
		 */		
		case GET_WORD_ADR_7BITS:
			Detect_START();
			Detect_STOP();

			/* look for SCL LOW to HIGH transition */
			if (!eeprom.old_scl && eeprom.scl)
			{
				if (eeprom.cycles == 0) eeprom.cycles ++;
			}
				

			/* look for SCL HIGH to LOW transition */
			if (eeprom.old_scl && !eeprom.scl && (eeprom.cycles > 0))
			{				
				if (eeprom.cycles < 8) eeprom.word_address |= (eeprom.old_sda << (7 - eeprom.cycles));
				else if (eeprom.cycles == 8) eeprom.rw = eeprom.old_sda;
				else
				{	/* ACK CYCLE */
					eeprom.cycles = 0;
					eeprom.word_address &= eeprom.type.size_mask;
					eeprom.state = eeprom.rw ? READ_DATA : WRITE_DATA;
				}

				eeprom.cycles ++;
			}
			break;


		/* Get Slave Address (3bits) : MODE-2 & MODE-3 only (24C01 - 24C512) (0-3bits, depending on the array size)
		 * or/and Word Address MSB: MODE-2 only (24C04 - 24C16) (0-3bits, depending on the array size)
		 * and R/W bit
		 */		
		case GET_SLAVE_ADR:

			Detect_START();
			Detect_STOP();

			/* look for SCL LOW to HIGH transition */
			if (!eeprom.old_scl && eeprom.scl)
			{
				if (eeprom.cycles == 0) eeprom.cycles ++;
			}

			/* look for SCL HIGH to LOW transition */
			if (eeprom.old_scl && !eeprom.scl && (eeprom.cycles > 0))
			{
				if ((eeprom.cycles > 4) && (eeprom.cycles <8))
				{
					if ((eeprom.type.address_bits == 16) ||
						(eeprom.type.size_mask < (1 << (15 - eeprom.cycles))))
					{
						/* this is a SLAVE ADDRESS bit */
						eeprom.slave_mask |= (eeprom.old_sda << (7 - eeprom.cycles));
					}
					else
					{
						/* this is a WORD ADDRESS high bit */
						if (eeprom.old_sda) eeprom.word_address |= (1 << (15 - eeprom.cycles));
						else eeprom.word_address &= ~(1 << (15 - eeprom.cycles));
					}
				}
				else if (eeprom.cycles == 8) eeprom.rw = eeprom.old_sda;
				else if (eeprom.cycles > 8)
				{
					/* ACK CYCLE */
					eeprom.cycles = 0;
					if (eeprom.type.address_bits == 16)
					{
						/* two ADDRESS bytes */
						eeprom.state = eeprom.rw ? READ_DATA : GET_WORD_ADR_HIGH;
						eeprom.slave_mask <<= 16;
					}
					else
					{
						/* one ADDRESS byte */
						eeprom.state = eeprom.rw ? READ_DATA : GET_WORD_ADR_LOW;
						eeprom.slave_mask <<= 8;
					}
				}

				eeprom.cycles ++;
			}
			break;

		/* Get Word Address MSB (4-8bits depending on the array size)
		 * MODE-3 only (24C32 - 24C512)
		 */
		case GET_WORD_ADR_HIGH:

			Detect_START();
			Detect_STOP();

			/* look for SCL HIGH to LOW transition */
			if (eeprom.old_scl && !eeprom.scl)
			{				
				if (eeprom.cycles < 9)
				{
					if ((eeprom.type.size_mask + 1) < (1 << (17 - eeprom.cycles)))
					{
						/* ignored bit: slave mask should be right-shifted by one  */
						eeprom.slave_mask >>= 1;
					}
					else
					{
						/* this is a WORD ADDRESS high bit */
						if (eeprom.old_sda) eeprom.word_address |= (1 << (16 - eeprom.cycles));
						else eeprom.word_address &= ~(1 << (16 - eeprom.cycles));
					}

					eeprom.cycles ++;
				}
				else
				{
					/* ACK CYCLE */
					eeprom.cycles = 1;
					eeprom.state = GET_WORD_ADR_LOW;
				}
			}
			break;


		/* Get Word Address LSB: 7bits (24C01) or 8bits (24C02-24C512)
		 * MODE-2 and MODE-3 only (24C01 - 24C512)
		 */
		case GET_WORD_ADR_LOW: 

			Detect_START();
			Detect_STOP();

			/* look for SCL HIGH to LOW transition */
			if (eeprom.old_scl && !eeprom.scl)
			{
				if (eeprom.cycles < 9)
				{
					if ((eeprom.type.size_mask + 1) < (1 << (9 - eeprom.cycles)))
					{
						/* ignored bit (X24C01): slave mask should be right-shifted by one  */
						eeprom.slave_mask >>= 1;
					}
					else
					{
						/* this is a WORD ADDRESS high bit */
						if (eeprom.old_sda) eeprom.word_address |= (1 << (8 - eeprom.cycles));
						else eeprom.word_address &= ~(1 << (8 - eeprom.cycles));
					}

					eeprom.cycles ++;
				}
				else
				{
					/* ACK CYCLE */
					eeprom.cycles = 1;
					eeprom.word_address &= eeprom.type.size_mask;
					eeprom.state = WRITE_DATA;
				}
			}
			break;


		/*
		 * Read Cycle
		 */
		case READ_DATA:

			Detect_START();
			Detect_STOP();

			/* look for SCL HIGH to LOW transition */
			if (eeprom.old_scl && !eeprom.scl)
			{
				if (eeprom.cycles < 9) eeprom.cycles ++;
				else
				{
					eeprom.cycles = 1;

					/* ACK not received */
					if (eeprom.old_sda) eeprom.state = WAIT_STOP;
				 }
			}
			break;


		/*
		 * Write Cycle
		 */
		case WRITE_DATA:

			Detect_START();
			Detect_STOP();

			/* look for SCL HIGH to LOW transition */
			if (eeprom.old_scl && !eeprom.scl)
			{				
				if (eeprom.cycles < 9)
				{
					/* Write DATA bits (max 64kBytes) */
					sram_address = (eeprom.slave_mask | eeprom.word_address) & 0xFFFF;
					if (eeprom.old_sda) sram.sram[sram_address] |= (1 << (8 - eeprom.cycles));
					else sram.sram[sram_address] &= ~(1 << (8 - eeprom.cycles));

					if (eeprom.cycles == 8) 
					{
						/* WORD ADDRESS is incremented (roll up at maximum pagesize) */
						eeprom.word_address = (eeprom.word_address & (0xFFFF - eeprom.type.pagewrite_mask)) | 
											  ((eeprom.word_address + 1) & eeprom.type.pagewrite_mask);
					}

					eeprom.cycles ++;
				}
				else eeprom.cycles = 1;	/* ACK cycle */
			}
			break;
	}

	eeprom.old_scl = eeprom.scl;
	eeprom.old_sda = eeprom.sda;
}


unsigned int EEPROM_Read(unsigned int address)
{
	uint16 sram_address;
	uint8 sda_out = eeprom.sda;

	/* EEPROM state */
	switch (eeprom.state)
	{
		case READ_DATA:
			if (eeprom.cycles < 9)
			{
				/* Return DATA bits (max 64kBytes) */
				sram_address = (eeprom.slave_mask | eeprom.word_address) & 0xFFFF;
				sda_out = (sram.sram[sram_address] >> (8 - eeprom.cycles)) & 1;

				if (eeprom.cycles == 8)
				{
					/* WORD ADDRESS is incremented (roll up at maximum array size) */
					eeprom.word_address ++;
					eeprom.word_address &= eeprom.type.size_mask;
				}
			}
			break;

		case GET_WORD_ADR_7BITS:
		case GET_SLAVE_ADR:
		case GET_WORD_ADR_HIGH:
		case GET_WORD_ADR_LOW:
		case WRITE_DATA:
			if (eeprom.cycles == 9) sda_out = 0;
			break;

		default:
			break;
	}

	if (address == eeprom.type.sda_out_adr) return (sda_out << eeprom.type.sda_out_bit);
	else return 0;
}