86 lines
1.8 KiB
C#
86 lines
1.8 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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F0 (MegaBoy)
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-----
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This was used on one game, "MegaBoy".. Some kind of educational cartridge. It supports
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64K of ROM making it the biggest single production game made during the original run
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of the 2600.
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Bankswitching is very simple. There's 16 4K banks, and accessing 1FF0 causes the bank
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number to increment.
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This means that you must keep accessing 1FF0 until the bank you want is selected. Each
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bank is numbered by means of one of the ROM locations, and the code simply keeps accessing
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1FF0 until the bank it is looking for comes up.
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*/
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internal sealed class mF0 : MapperBase
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{
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private int _bank;
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public mF0(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("bank", ref _bank);
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}
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public override void HardReset()
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{
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_bank = 0;
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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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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 byte ReadMem(ushort addr, bool peek)
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{
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if (!peek)
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{
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if (addr == 0x1FF0)
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{
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Increment();
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}
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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[(_bank << 12) + (addr & 0xFFF)];
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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 (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 == 0x1ff0 && !poke)
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{
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Increment();
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}
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}
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private void Increment()
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{
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_bank++;
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_bank &= 0x0F;
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}
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}
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}
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