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/*===================================================================*/
/* */
/* Mapper 251 */
/* */
/*===================================================================*/
BYTE Map251_Reg[11];
BYTE Map251_Breg[4];
/*-------------------------------------------------------------------*/
/* Initialize Mapper 251 */
/*-------------------------------------------------------------------*/
void Map251_Init()
{
/* Initialize Mapper */
MapperInit = Map251_Init;
/* Write to Mapper */
MapperWrite = Map251_Write;
/* Write to SRAM */
MapperSram = Map251_Sram;
/* Write to APU */
MapperApu = Map0_Apu;
/* Read from APU */
MapperReadApu = Map0_ReadApu;
/* Callback at VSync */
MapperVSync = Map0_VSync;
/* Callback at HSync */
MapperHSync = Map0_HSync;
/* Callback at PPU */
MapperPPU = Map0_PPU;
/* Callback at Rendering Screen ( 1:BG, 0:Sprite ) */
MapperRenderScreen = Map0_RenderScreen;
/* Set SRAM Banks */
SRAMBANK = SRAM;
/* Set ROM Banks */
ROMBANK0 = ROMPAGE( 0 );
ROMBANK1 = ROMPAGE( 1 );
ROMBANK2 = ROMLASTPAGE( 1 );
ROMBANK3 = ROMLASTPAGE( 0 );
/* Set Registers */
InfoNES_Mirroring( 1 );
int i;
for( i = 0; i < 11; i++ )
Map251_Reg[i] = 0;
for( i = 0; i < 4; i++ )
Map251_Breg[i] = 0;
/* Set up wiring of the interrupt pin */
K6502_Set_Int_Wiring( 1, 1 );
}
/*-------------------------------------------------------------------*/
/* Mapper 251 Write Function */
/*-------------------------------------------------------------------*/
void Map251_Write( WORD wAddr, BYTE byData )
{
switch( wAddr & 0xE001 ) {
case 0x8000:
Map251_Reg[8] = byData;
Map251_Set_Banks();
break;
case 0x8001:
Map251_Reg[Map251_Reg[8]&0x07] = byData;
Map251_Set_Banks();
break;
case 0xA001:
if( byData & 0x80 ) {
Map251_Reg[ 9] = 1;
Map251_Reg[10] = 0;
} else {
Map251_Reg[ 9] = 0;
}
break;
}
}
/*-------------------------------------------------------------------*/
/* Mapper 251 Write to SRAM Function */
/*-------------------------------------------------------------------*/
void Map251_Sram( WORD wAddr, BYTE byData )
{
if( (wAddr & 0xE001) == 0x6000 ) {
if( Map251_Reg[9] ) {
Map251_Breg[Map251_Reg[10]++] = byData;
if( Map251_Reg[10] == 4 ) {
Map251_Reg[10] = 0;
Map251_Set_Banks();
}
}
}
}
/*-------------------------------------------------------------------*/
/* Mapper 251 Set Banks Function */
/*-------------------------------------------------------------------*/
void Map251_Set_Banks()
{
int nChr[6];
int nPrg[4];
for( int i = 0; i < 6; i++ ) {
nChr[i] = (Map251_Reg[i]|(Map251_Breg[1]<<4)) & ((Map251_Breg[2]<<4)|0x0F);
}
if( Map251_Reg[8] & 0x80 ) {
PPUBANK[ 0 ] = VROMPAGE(nChr[2] % (NesHeader.byVRomSize<<3));
PPUBANK[ 1 ] = VROMPAGE(nChr[3] % (NesHeader.byVRomSize<<3));
PPUBANK[ 2 ] = VROMPAGE(nChr[4] % (NesHeader.byVRomSize<<3));
PPUBANK[ 3 ] = VROMPAGE(nChr[5] % (NesHeader.byVRomSize<<3));
PPUBANK[ 4 ] = VROMPAGE(nChr[0] % (NesHeader.byVRomSize<<3));
PPUBANK[ 5 ] = VROMPAGE((nChr[0]+1) % (NesHeader.byVRomSize<<3));
PPUBANK[ 6 ] = VROMPAGE(nChr[1] % (NesHeader.byVRomSize<<3));
PPUBANK[ 7 ] = VROMPAGE((nChr[1]+1) % (NesHeader.byVRomSize<<3));
InfoNES_SetupChr();
} else {
PPUBANK[ 0 ] = VROMPAGE(nChr[0] % (NesHeader.byVRomSize<<3));
PPUBANK[ 1 ] = VROMPAGE((nChr[0]+1) % (NesHeader.byVRomSize<<3));
PPUBANK[ 2 ] = VROMPAGE(nChr[1] % (NesHeader.byVRomSize<<3));
PPUBANK[ 3 ] = VROMPAGE((nChr[1]+1) % (NesHeader.byVRomSize<<3));
PPUBANK[ 4 ] = VROMPAGE(nChr[2] % (NesHeader.byVRomSize<<3));
PPUBANK[ 5 ] = VROMPAGE(nChr[3] % (NesHeader.byVRomSize<<3));
PPUBANK[ 6 ] = VROMPAGE(nChr[4] % (NesHeader.byVRomSize<<3));
PPUBANK[ 7 ] = VROMPAGE(nChr[5] % (NesHeader.byVRomSize<<3));
InfoNES_SetupChr();
}
nPrg[0] = (Map251_Reg[6]&((Map251_Breg[3]&0x3F)^0x3F))|(Map251_Breg[1]);
nPrg[1] = (Map251_Reg[7]&((Map251_Breg[3]&0x3F)^0x3F))|(Map251_Breg[1]);
nPrg[2] = nPrg[3] =((Map251_Breg[3]&0x3F)^0x3F)|(Map251_Breg[1]);
nPrg[2] &= (NesHeader.byRomSize<<1)-1;
if( Map251_Reg[8] & 0x40 ) {
ROMBANK0 = ROMPAGE(nPrg[2] % (NesHeader.byRomSize<<1));
ROMBANK1 = ROMPAGE(nPrg[1] % (NesHeader.byRomSize<<1));
ROMBANK2 = ROMPAGE(nPrg[0] % (NesHeader.byRomSize<<1));
ROMBANK3 = ROMPAGE(nPrg[3] % (NesHeader.byRomSize<<1));
} else {
ROMBANK0 = ROMPAGE(nPrg[0] % (NesHeader.byRomSize<<1));
ROMBANK1 = ROMPAGE(nPrg[1] % (NesHeader.byRomSize<<1));
ROMBANK2 = ROMPAGE(nPrg[2] % (NesHeader.byRomSize<<1));
ROMBANK3 = ROMPAGE(nPrg[3] % (NesHeader.byRomSize<<1));
}
}
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