85 lines
1.6 KiB
C#
85 lines
1.6 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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F6 (Atari style 16K)
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-----
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This is a fairly standard 16K bankswitching method. It works like F8, except there's
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four 4K banks of ROM, selected by accessing 1FF6 through 1FF9. These sequentially
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select one of the 4 banks. i.e. 1FF6 selects bank 0, 1FF7 selects bank 1, etc.
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*/
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internal class mF6 : MapperBase
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{
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private int _toggle;
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public mF6(Atari2600 core) : base(core)
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{
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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("toggle", ref _toggle);
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}
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public override void HardReset()
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{
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_toggle = 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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return Core.Rom[(_toggle << 12) + (addr & 0xFFF)];
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}
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public override byte ReadMemory(ushort addr) => ReadMem(addr, false);
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public override byte PeekMemory(ushort addr) => ReadMem(addr, true);
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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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=> WriteMem(addr, value, false);
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public override void PokeMemory(ushort addr, byte value)
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=> WriteMem(addr, value, true);
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private void Address(ushort addr)
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{
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_toggle = addr switch
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{
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0x1FF6 => 0,
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0x1FF7 => 1,
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0x1FF8 => 2,
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0x1FF9 => 3,
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_ => _toggle
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};
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}
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}
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}
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