Path: blob/master/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper0020.cs
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using System;
using System.Collections.Generic;
using System.Linq;
using BizHawk.Common;
namespace BizHawk.Emulation.Cores.Computers.Commodore64.Cartridge
{
// EasyFlash cartridge
// No official games came on one of these but there
// are a few dumps from GameBase64 that use this mapper
// There are 64 banks total, DE00 is bank select.
// Selecing a bank will select both Lo and Hi ROM.
// DE02 will switch exrom/game bits: bit 0=game,
// bit 1=exrom, bit 2=for our cases, always set true.
// These two registers are write only.
// This cartridge always starts up in Ultimax mode,
// with Game set high and ExRom set low.
// There is also 256 bytes RAM at DF00-DFFF.
// We emulate having the AM29F040 chip.
public abstract partial class CartridgeDevice
{
private sealed class Mapper0020 : CartridgeDevice
{
[SaveState.SaveWithName("BankOffset")]
private int _bankOffset = 63 << 13;
[SaveState.DoNotSave]
private int[] _banksA = new int[64 << 13]; //8000
[SaveState.DoNotSave]
private int[] _banksB = new int[64 << 13]; //A000
[SaveState.DoNotSave]
private readonly int[] _originalMediaA; //8000
[SaveState.DoNotSave]
private readonly int[] _originalMediaB; //A000
[SaveState.SaveWithName("BoardLed")]
private bool _boardLed;
[SaveState.SaveWithName("Jumper")]
private bool _jumper = false;
[SaveState.SaveWithName("StateBits")]
private int _stateBits;
[SaveState.SaveWithName("RAM")]
private readonly int[] _ram = new int[256];
[SaveState.SaveWithName("CommandLatch55")]
private bool _commandLatch55;
[SaveState.SaveWithName("CommandLatchAA")]
private bool _commandLatchAa;
[SaveState.SaveWithName("InternalROMState")]
private int _internalRomState;
public Mapper0020(IList<int> newAddresses, IList<int> newBanks, IList<int[]> newData)
{
DriveLightEnabled = true;
var count = newAddresses.Count;
// force ultimax mode (the cart SHOULD set this
// otherwise on load, according to the docs)
pinGame = false;
pinExRom = true;
// for safety, initialize all banks to dummy
for (var i = 0; i < 64*0x2000; i++)
{
_banksA[i] = 0xFF;
_banksB[i] = 0xFF;
}
// load in all banks
for (var i = 0; i < count; i++)
{
switch (newAddresses[i])
{
case 0x8000:
Array.Copy(newData[i], 0, _banksA, newBanks[i] * 0x2000, 0x2000);
break;
case 0xA000:
case 0xE000:
Array.Copy(newData[i], 0, _banksB, newBanks[i] * 0x2000, 0x2000);
break;
}
}
// default to bank 0
BankSet(0);
// internal operation settings
_commandLatch55 = false;
_commandLatchAa = false;
_internalRomState = 0;
// back up original media
_originalMediaA = _banksA.Select(d => d).ToArray();
_originalMediaB = _banksB.Select(d => d).ToArray();
}
private void BankSet(int index)
{
_bankOffset = (index & 0x3F) << 13;
}
public override int Peek8000(int addr)
{
addr &= 0x1FFF;
return _banksA[addr | _bankOffset];
}
public override int PeekA000(int addr)
{
addr &= 0x1FFF;
return _banksB[addr | _bankOffset];
}
public override int PeekDE00(int addr)
{
// normally you can't read these regs
// but Peek is provided here for debug reasons
// and may not stay around
addr &= 0x02;
return addr == 0x00 ? _bankOffset >> 13 : _stateBits;
}
public override int PeekDF00(int addr)
{
addr &= 0xFF;
return _ram[addr];
}
public override void PokeDE00(int addr, int val)
{
addr &= 0x02;
if (addr == 0x00)
BankSet(val);
else
StateSet(val);
}
public override void PokeDF00(int addr, int val)
{
addr &= 0xFF;
_ram[addr] = val & 0xFF;
}
public override int Read8000(int addr)
{
return ReadInternal(addr & 0x1FFF, _banksA);
}
public override int ReadA000(int addr)
{
return ReadInternal(addr & 0x1FFF, _banksB);
}
public override int ReadDF00(int addr)
{
addr &= 0xFF;
return _ram[addr];
}
private int ReadInternal(int addr, int[] bank)
{
switch (_internalRomState)
{
case 0x80:
break;
case 0x90:
switch (addr & 0x1FFF)
{
case 0x0000:
return 0x01;
case 0x0001:
return 0xA4;
case 0x0002:
return 0x00;
}
break;
case 0xA0:
break;
case 0xF0:
break;
}
return bank[addr | _bankOffset];
}
private void StateSet(int val)
{
_stateBits = val &= 0x87;
if ((val & 0x04) != 0)
pinGame = (val & 0x01) == 0;
else
pinGame = _jumper;
pinExRom = (val & 0x02) == 0;
_boardLed = (val & 0x80) != 0;
_internalRomState = 0;
DriveLightOn = _boardLed;
}
public override void Write8000(int addr, int val)
{
WriteInternal(addr, val);
}
public override void WriteA000(int addr, int val)
{
WriteInternal(addr | 0x2000, val);
}
private void WriteInternal(int addr, int val)
{
if (pinGame || !pinExRom)
{
return;
}
if (val == 0xF0) // any address, resets flash
{
_internalRomState = 0;
_commandLatch55 = false;
_commandLatchAa = false;
}
else if (_internalRomState != 0x00 && _internalRomState != 0xF0)
{
switch (_internalRomState)
{
case 0xA0:
if ((addr & 0x2000) == 0)
{
addr &= 0x1FFF;
_banksA[addr | _bankOffset] = val & 0xFF;
}
else
{
addr &= 0x1FFF;
_banksB[addr | _bankOffset] = val & 0xFF;
}
break;
}
}
else if (addr == 0x0555) // $8555
{
if (!_commandLatchAa)
{
if (val == 0xAA)
{
_commandLatch55 = true;
}
}
else
{
// process EZF command
_internalRomState = val;
}
}
else if (addr == 0x02AA) // $82AA
{
if (_commandLatch55 && val == 0x55)
{
_commandLatchAa = true;
}
else
{
_commandLatch55 = false;
}
}
else
{
_commandLatch55 = false;
_commandLatchAa = false;
}
}
public override void WriteDE00(int addr, int val)
{
addr &= 0x02;
if (addr == 0x00)
BankSet(val);
else
StateSet(val);
}
public override void WriteDF00(int addr, int val)
{
_ram[addr] = val & 0xFF;
}
public override void SyncState(Serializer ser)
{
SaveState.SyncDelta("MediaStateA", ser, _originalMediaA, ref _banksA);
SaveState.SyncDelta("MediaStateB", ser, _originalMediaB, ref _banksB);
base.SyncState(ser);
DriveLightOn = _boardLed;
}
}
}
}