112 lines
2.3 KiB
C#
112 lines
2.3 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 sealed class mEFSC : MapperBase
|
|
{
|
|
private int _bank4K;
|
|
private byte[] _ram = new byte[128];
|
|
|
|
public mEFSC(Atari2600 core) : base(core)
|
|
{
|
|
}
|
|
|
|
public override byte[] CartRam => _ram;
|
|
|
|
public override void SyncState(Serializer ser)
|
|
{
|
|
base.SyncState(ser);
|
|
ser.Sync("bank4k", ref _bank4K);
|
|
ser.Sync("auxRam", ref _ram, false);
|
|
}
|
|
|
|
public override void HardReset()
|
|
{
|
|
_bank4K = 0;
|
|
_ram = new byte[128];
|
|
}
|
|
|
|
public override byte ReadMemory(ushort addr) => ReadMem(addr, false);
|
|
|
|
public override byte PeekMemory(ushort addr) => ReadMem(addr, true);
|
|
|
|
public override void WriteMemory(ushort addr, byte value)
|
|
=> WriteMem(addr, value, false);
|
|
|
|
public override void PokeMemory(ushort addr, byte value)
|
|
=> WriteMem(addr, value, true);
|
|
|
|
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
|
|
}
|
|
|
|
if (addr < 0x1100)
|
|
{
|
|
return _ram[addr & 0x7F];
|
|
}
|
|
|
|
return Core.Rom[(_bank4K << 12) + (addr & 0xFFF)];
|
|
}
|
|
|
|
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;
|
|
}
|
|
}
|
|
|
|
private void Address(ushort addr)
|
|
{
|
|
_bank4K = addr switch
|
|
{
|
|
0x1FE0 => 0,
|
|
0x1FE1 => 1,
|
|
0x1FE2 => 2,
|
|
0x1FE3 => 3,
|
|
0x1FE4 => 4,
|
|
0x1FE5 => 5,
|
|
0x1FE6 => 6,
|
|
0x1FE7 => 7,
|
|
0x1FE8 => 8,
|
|
0x1FE9 => 9,
|
|
0x1FEA => 10,
|
|
0x1FEB => 11,
|
|
0x1FEC => 12,
|
|
0x1FED => 13,
|
|
0x1FEE => 14,
|
|
0x1FEF => 15,
|
|
_ => _bank4K
|
|
};
|
|
}
|
|
}
|
|
}
|