109 lines
2.0 KiB
C#
109 lines
2.0 KiB
C#
using BizHawk.Common;
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namespace BizHawk.Emulation.Cores.Atari.Atari2600
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{
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/**
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This is an extended version of the CBS RAM Plus bankswitching scheme
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supported by the Harmony cartridge.
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There are six (or seven) 4K banks and 256 bytes of RAM.
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*/
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internal class mFA2 : MapperBase
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{
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private int _bank4k;
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private ByteBuffer _ram = new ByteBuffer(256);
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public override bool HasCartRam
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{
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get { return true; }
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}
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public override ByteBuffer CartRam
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{
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get { return _ram; }
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}
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public override void SyncState(Serializer ser)
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{
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base.SyncState(ser);
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ser.Sync("bank4k", ref _bank4k);
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ser.Sync("auxRam", ref _ram);
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}
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public override void Dispose()
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{
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base.Dispose();
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_ram.Dispose();
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}
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public override void HardReset()
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{
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_bank4k = 0;
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_ram = new ByteBuffer(256);
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base.HardReset();
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}
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private byte ReadMem(ushort addr, bool peek)
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{
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if (!peek)
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{
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Address(addr);
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}
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if (addr < 0x1000)
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{
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return base.ReadMemory(addr);
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}
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if (addr < 0x1100)
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{
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return 0xFF;
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}
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if (addr < 0x1200)
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{
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return _ram[addr & 0xFF];
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}
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return Core.Rom[(_bank4k << 12) + (addr & 0xFFF)];
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}
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public override byte ReadMemory(ushort addr)
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{
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return ReadMem(addr, false);
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}
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public override byte PeekMemory(ushort addr)
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{
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return ReadMem(addr, true);
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}
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public override void WriteMemory(ushort addr, byte value)
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{
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Address(addr);
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if (addr < 0x1000)
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{
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base.WriteMemory(addr, value);
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}
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else if (addr < 0x1100)
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{
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_ram[addr & 0xFF] = value;
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}
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}
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private void Address(ushort addr)
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{
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if (addr == 0x1FF5) _bank4k = 0;
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if (addr == 0x1FF6) _bank4k = 1;
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if (addr == 0x1FF7) _bank4k = 2;
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if (addr == 0x1FF8) _bank4k = 3;
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if (addr == 0x1FF9) _bank4k = 4;
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if (addr == 0x1FFA) _bank4k = 5;
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if (addr == 0x1FFB && Core.Rom.Length == 28 * 1024) // Only available on 28k Roms
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{
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_bank4k = 6;
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}
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}
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}
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}
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