mirror of https://github.com/bsnes-emu/bsnes.git
62 lines
1.7 KiB
C++
62 lines
1.7 KiB
C++
auto Cartridge::MBC2::read(uint16 address) -> uint8 {
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if((address & 0xc000) == 0x0000) { //$0000-3fff
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return cartridge.rom.read(address.bits(0,13));
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}
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if((address & 0xc000) == 0x4000) { //$4000-7fff
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return cartridge.rom.read(io.rom.bank << 14 | address.bits(0,13));
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}
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if((address & 0xee01) == 0xa000) { //$a000-a1ff (even)
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if(!io.ram.enable) return 0xff;
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auto ram = cartridge.ram.read(address.bits(1,8));
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return 0xf0 | ram.bits(0,3);
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}
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if((address & 0xee01) == 0xa001) { //$a000-a1ff (odd)
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if(!io.ram.enable) return 0xff;
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auto ram = cartridge.ram.read(address.bits(1,8));
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return 0xf0 | ram.bits(4,7);
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}
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return 0xff;
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}
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auto Cartridge::MBC2::write(uint16 address, uint8 data) -> void {
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if((address & 0xe000) == 0x0000) { //$0000-1fff
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if(!address.bit(8)) io.ram.enable = data.bits(0,3) == 0x0a;
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return;
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}
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if((address & 0xe000) == 0x2000) { //$2000-3fff
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if(address.bit(8)) io.rom.bank = data.bits(0,3);
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if(!io.rom.bank) io.rom.bank = 0x01;
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return;
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}
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if((address & 0xee01) == 0xa000) { //$a000-a1ff (even)
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if(!io.ram.enable) return;
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auto ram = cartridge.ram.read(address.bits(1,8));
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ram.bits(0,3) = data.bits(0,3);
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cartridge.ram.write(address.bits(1,8), ram);
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return;
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}
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if((address & 0xee01) == 0xa001) { //$a000-a1ff (odd)
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if(!io.ram.enable) return;
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auto ram = cartridge.ram.read(address.bits(1,8));
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ram.bits(4,7) = data.bits(0,3);
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cartridge.ram.write(address.bits(1,8), ram);
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return;
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}
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}
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auto Cartridge::MBC2::power() -> void {
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io = {};
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}
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auto Cartridge::MBC2::serialize(serializer& s) -> void {
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s.integer(io.rom.bank);
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s.integer(io.ram.enable);
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}
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