128 lines
2.7 KiB
C#
128 lines
2.7 KiB
C#
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;
|
|
}
|
|
}
|
|
}
|