91 lines
2.1 KiB
C++
91 lines
2.1 KiB
C++
#ifdef _NES_MAPPER_CPP_
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/////////////////////////////////////////////////////////////////////
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// Mapper 255
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void NES_mapper255::Reset()
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{
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// set CPU bank pointers
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set_CPU_banks(0,1,2,3);
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// set PPU bank pointers
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set_PPU_banks(0,1,2,3,4,5,6,7);
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set_mirroring(NES_PPU::MIRROR_VERT);
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//regs[0] = regs[2] = 0x0F;
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//regs[1] = regs[3] = 0x00;
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}
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uint8 NES_mapper255::MemoryReadLow(uint32 addr)
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{
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if(addr >= 0x5800)
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{
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return regs[addr & 0x0003] & 0x0F;
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}
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else
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{
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return (uint8)(addr >> 8);
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}
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}
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void NES_mapper255::MemoryWriteLow(uint32 addr, uint8 data)
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{
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if(addr >= 0x5800)
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{
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regs[addr & 0x0003] = data & 0x0F;
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}
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}
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void NES_mapper255::MemoryWrite(uint32 addr, uint8 data)
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{
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uint8 prg_bank = (uint8)((addr & 0x0F80) >> 7);
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uint8 chr_bank = (uint8)(addr & 0x003F);
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uint8 rom_bank = (uint8)((addr & 0x4000) >> 14);
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if(addr & 0x2000)
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{
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set_mirroring(NES_PPU::MIRROR_HORIZ);
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}
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else
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{
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set_mirroring(NES_PPU::MIRROR_VERT);
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}
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if(addr & 0x1000)
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{//16K PRG_ROM
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if(addr & 0x0040)
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{//upper half
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set_CPU_bank4(0x80*rom_bank+prg_bank*4+2);
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set_CPU_bank5(0x80*rom_bank+prg_bank*4+3);
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set_CPU_bank6(0x80*rom_bank+prg_bank*4+2);
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set_CPU_bank7(0x80*rom_bank+prg_bank*4+3);
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}
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else
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{//lower half
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set_CPU_bank4(0x80*rom_bank+prg_bank*4+0);
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set_CPU_bank5(0x80*rom_bank+prg_bank*4+1);
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set_CPU_bank6(0x80*rom_bank+prg_bank*4+0);
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set_CPU_bank7(0x80*rom_bank+prg_bank*4+1);
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}
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}
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else
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{//32K PRG_ROM
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set_CPU_bank4(0x80*rom_bank+prg_bank*4+0);
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set_CPU_bank5(0x80*rom_bank+prg_bank*4+1);
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set_CPU_bank6(0x80*rom_bank+prg_bank*4+2);
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set_CPU_bank7(0x80*rom_bank+prg_bank*4+3);
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}
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set_PPU_bank0(0x200*rom_bank+chr_bank*8+0);
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set_PPU_bank1(0x200*rom_bank+chr_bank*8+1);
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set_PPU_bank2(0x200*rom_bank+chr_bank*8+2);
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set_PPU_bank3(0x200*rom_bank+chr_bank*8+3);
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set_PPU_bank4(0x200*rom_bank+chr_bank*8+4);
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set_PPU_bank5(0x200*rom_bank+chr_bank*8+5);
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set_PPU_bank6(0x200*rom_bank+chr_bank*8+6);
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set_PPU_bank7(0x200*rom_bank+chr_bank*8+7);
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}
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/////////////////////////////////////////////////////////////////////
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#endif
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