193 lines
3.6 KiB
C#
193 lines
3.6 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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E0 (Parker Bros)
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-----
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Parker Brothers used this, and it was used on one other game (Tooth Protectors). It
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uses 8K of ROM and can map 1K sections of it.
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This mapper has 4 1K banks of ROM in the address space. The address space is broken up
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into the following locations:
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1000-13FF : To select a 1K ROM bank here, access 1FE0-1FE7 (1FE0 = select first 1K, etc)
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1400-17FF : To select a 1K ROM bank, access 1FE8-1FEF
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1800-1BFF : To select a 1K ROM bank, access 1FF0-1FF7
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1C00-1FFF : This is fixed to the last 1K ROM bank of the 8K
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Like F8, F6, etc. accessing one of the locations indicated will perform the switch.
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Example Games:
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Frogger II - Threedeep! (1983) (Parker Bros)
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*/
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internal class mE0 : MapperBase
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{
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private int _toggle1;
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private int _toggle2;
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private int _toggle3;
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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("toggle1", ref _toggle1);
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ser.Sync("toggle2", ref _toggle2);
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ser.Sync("toggle3", ref _toggle3);
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}
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public override void HardReset()
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{
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_toggle1 = 0;
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_toggle2 = 0;
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_toggle3 = 0;
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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 < 0x1400)
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{
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return Core.Rom[(_toggle1 << 10) + (addr & 0x3FF)];
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}
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if (addr < 0x1800)
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{
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return Core.Rom[(_toggle2 << 10) + (addr & 0x3FF)];
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}
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if (addr < 0x1C00)
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{
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return Core.Rom[(_toggle3 << 10) + (addr & 0x3FF)];
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}
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return Core.Rom[(7 * 1024) + (addr & 0x3FF)]; // 7 because final bank is always set to last
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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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private void WriteMem(ushort addr, byte value, bool poke)
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{
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if (!poke)
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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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base.WriteMemory(addr, value);
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}
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}
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public override void WriteMemory(ushort addr, byte value)
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{
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WriteMem(addr, value, poke: false);
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}
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public override void PokeMemory(ushort addr, byte value)
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{
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WriteMem(addr, value, poke: true);
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}
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private void Address(ushort addr)
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{
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switch (addr)
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{
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case 0x1FE0:
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_toggle1 = 0;
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break;
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case 0x1FE1:
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_toggle1 = 1;
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break;
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case 0x1FE2:
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_toggle1 = 2;
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break;
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case 0x1FE3:
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_toggle1 = 3;
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break;
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case 0x1FE4:
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_toggle1 = 4;
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break;
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case 0x1FE5:
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_toggle1 = 5;
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break;
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case 0x1FE6:
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_toggle1 = 6;
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break;
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case 0x1FE7:
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_toggle1 = 7;
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break;
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case 0x1FE8:
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_toggle2 = 0;
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break;
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case 0x1FE9:
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_toggle2 = 1;
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break;
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case 0x1FEA:
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_toggle2 = 2;
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break;
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case 0x1FEB:
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_toggle2 = 3;
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break;
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case 0x1FEC:
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_toggle2 = 4;
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break;
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case 0x1FED:
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_toggle2 = 5;
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break;
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case 0x1FEE:
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_toggle2 = 6;
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break;
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case 0x1FEF:
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_toggle2 = 7;
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break;
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case 0x1FF0:
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_toggle3 = 0;
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break;
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case 0x1FF1:
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_toggle3 = 1;
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break;
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case 0x1FF2:
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_toggle3 = 2;
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break;
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case 0x1FF3:
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_toggle3 = 3;
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break;
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case 0x1FF4:
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_toggle3 = 4;
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break;
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case 0x1FF5:
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_toggle3 = 5;
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break;
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case 0x1FF6:
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_toggle3 = 6;
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break;
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case 0x1FF7:
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_toggle3 = 7;
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break;
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}
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}
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}
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}
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