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Atari 2600 - implement mapper F6SC, and slight fix to F8SC (uncomment read of write port emulation)

This commit is contained in:
adelikat 2014-04-04 23:49:03 +00:00
parent d79067c33c
commit 3d1e6ca830
2 changed files with 73 additions and 12 deletions
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72
BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF6SC.cs
View File

@ -1,16 +1,78 @@
using System;
using BizHawk.Common;
namespace BizHawk.Emulation.Cores.Atari.Atari2600
{
/**
Cartridge class used for Atari's 32K bankswitched games with
128 bytes of RAM. There are eight 4K banks.
Cartridge class used for Atari's 16K bankswitched games with
128 bytes of RAM. There are four 4K banks.
*/
internal class mF6SC : MapperBase
{
public mF6SC()
private int _bank4k;
private ByteBuffer _ram = new ByteBuffer(128);
private byte ReadMem(ushort addr, bool peek)
{
throw new NotImplementedException();
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);
}
public override void WriteMemory(ushort addr, byte value)
{
Address(addr);
if (addr < 0x1000)
{
base.WriteMemory(addr, value);
}
else if ((addr & 0x0FFF) < 0x80)
{
_ram[addr & 0x7F] = value;
}
}
public override void SyncState(Serializer ser)
{
base.SyncState(ser);
ser.Sync("bank_4k", ref _bank4k);
ser.Sync("auxRam", ref _ram);
}
private void Address(ushort addr)
{
if (addr == 0x1FF6) _bank4k = 0;
if (addr == 0x1FF7) _bank4k = 1;
if (addr == 0x1FF8) _bank4k = 2;
if (addr == 0x1FF9) _bank4k = 3;
}
}
}

13
BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF8SC.cs
View File

@ -23,13 +23,12 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
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)
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)];
}