using BizHawk.Common; namespace BizHawk.Emulation.Cores.Atari.Atari2600 { /** Cartridge class used for Homestar Runner by Paul Slocum. There are 16 4K banks (total of 64K ROM) with 128 bytes of RAM. Accessing $1FE0 - $1FEF switches to each bank. */ internal class mEFSC : MapperBase { private int _bank4k; private ByteBuffer _ram = new ByteBuffer(128); public override bool HasCartRam { get { return true; } } public override ByteBuffer CartRam { get { return _ram; } } public override void SyncState(Serializer ser) { base.SyncState(ser); ser.Sync("bank4k", ref _bank4k); ser.Sync("auxRam", ref _ram); } public override void Dispose() { base.Dispose(); _ram.Dispose(); } public override void HardReset() { _bank4k = 0; _ram = new ByteBuffer(128); base.HardReset(); } private byte ReadMem(ushort addr, bool peek) { if (!peek) { Address(addr); } if (addr < 0x1000) { return base.ReadMemory(addr); } if (addr < 0x1080) { _ram[(addr & 0x7F)] = 0xFF; // Reading from the write port triggers an unwanted write of open bus return 0xFF; // 0xFF is used for deterministic emulation, in reality it would be a random value based on pins being high or low } else if (addr < 0x1100) { return _ram[(addr & 0x7F)]; } return Core.Rom[(_bank4k << 12) + (addr & 0xFFF)]; } public override byte ReadMemory(ushort addr) { return ReadMem(addr, false); } public override byte PeekMemory(ushort addr) { return ReadMem(addr, true); } private void WriteMem(ushort addr, byte value, bool poke) { if (!poke) { Address(addr); } if (addr < 0x1000) { base.WriteMemory(addr, value); } else if ((addr & 0x0FFF) < 0x80) { _ram[addr & 0x7F] = value; } } public override void WriteMemory(ushort addr, byte value) { WriteMem(addr, value, poke: false); } public override void PokeMemory(ushort addr, byte value) { WriteMem(addr, value, poke: true); } private void Address(ushort addr) { if (addr == 0x1FE0) _bank4k = 0; if (addr == 0x1FE1) _bank4k = 1; if (addr == 0x1FE2) _bank4k = 2; if (addr == 0x1FE3) _bank4k = 3; if (addr == 0x1FE4) _bank4k = 4; if (addr == 0x1FE5) _bank4k = 5; if (addr == 0x1FE6) _bank4k = 6; if (addr == 0x1FE7) _bank4k = 7; if (addr == 0x1FE8) _bank4k = 8; if (addr == 0x1FE9) _bank4k = 9; if (addr == 0x1FEA) _bank4k = 10; if (addr == 0x1FEB) _bank4k = 11; if (addr == 0x1FEC) _bank4k = 12; if (addr == 0x1FED) _bank4k = 13; if (addr == 0x1FEE) _bank4k = 14; if (addr == 0x1FEF) _bank4k = 15; } } }