Path: blob/master/BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Cia.cs
2 views
using BizHawk.Common;
using System;
namespace BizHawk.Emulation.Cores.Computers.Commodore64.MOS
{
public sealed partial class Cia
{
/*
Commodore CIA 6526 core.
Many thanks to:
- 6502.org for hosting the 6526 datasheet
http://archive.6502.org/datasheets/mos_6526_cia.pdf
- Christian Bauer for information on the delayed interrupt mechanism on the 6526
http://frodo.cebix.net/
*/
private enum TimerState
{
Stop = 0,
WaitThenCount = 1,
LoadThenStop = 2,
LoadThenCount = 3,
LoadThenWaitThenCount = 4,
Count = 5,
CountThenStop = 6
}
public Func<bool> ReadFlag = () => true;
public bool DelayedInterrupts = true;
private int _pra;
private int _prb;
private int _ddra;
private int _ddrb;
private int _ta;
private int _tb;
private int _latcha;
private int _latchb;
private int _tod10Ths;
private int _todSec;
private int _todMin;
private int _todHr;
private int _latch10Ths;
private int _latchSec;
private int _latchMin;
private int _latchHr;
private int _alm10Ths;
private int _almSec;
private int _almMin;
private int _almHr;
private int _sdr;
private int _icr;
private int _cra;
private int _crb;
private int _intMask;
private bool _todLatch;
private bool _taCntPhi2;
private bool _taCntCnt;
private bool _tbCntPhi2;
private bool _tbCntTa;
private bool _tbCntCnt;
private bool _taIrqNextCycle;
private bool _taPrb6NegativeNextCycle;
private bool _tbIrqNextCycle;
private bool _tbPrb7NegativeNextCycle;
private bool _hasNewCra;
private bool _hasNewCrb;
private TimerState _taState;
private TimerState _tbState;
private int _newCra;
private int _newCrb;
private bool _flagLatch;
[SaveState.DoNotSave] private bool _flagInput;
[SaveState.DoNotSave] private bool _taUnderflow;
private readonly Port _port;
[SaveState.DoNotSave] private int _todlo;
[SaveState.DoNotSave] private int _todhi;
[SaveState.DoNotSave] private readonly int _todNum;
[SaveState.DoNotSave] private readonly int _todDen;
private int _todCounter;
private Cia(int todNum, int todDen)
{
_todNum = todNum;
_todDen = todDen;
}
public Cia(int todNum, int todDen, Func<bool[]> keyboard, Func<bool[]> joysticks) : this(todNum, todDen)
{
_port = new JoystickKeyboardPort(joysticks, keyboard);
}
public Cia(int todNum, int todDen, Func<int> readIec) : this(todNum, todDen)
{
_port = new IecPort(readIec);
}
public void HardReset()
{
_pra = 0;
_prb = 0;
_ddra = 0;
_ddrb = 0;
_ta = 0xFFFF;
_tb = 0xFFFF;
_latcha = 1;
_latchb = 1;
_tod10Ths = 0;
_todSec = 0;
_todMin = 0;
_todHr = 0;
_alm10Ths = 0;
_almSec = 0;
_almMin = 0;
_almHr = 0;
_sdr = 0;
_icr = 0;
_cra = 0;
_crb = 0;
_intMask = 0;
_todLatch = false;
_taCntPhi2 = false;
_taCntCnt = false;
_tbCntPhi2 = false;
_tbCntTa = false;
_tbCntCnt = false;
_taIrqNextCycle = false;
_tbIrqNextCycle = false;
_taState = TimerState.Stop;
_tbState = TimerState.Stop;
}
private void CheckIrqs()
{
if (_taIrqNextCycle)
{
_taIrqNextCycle = false;
TriggerInterrupt(1);
}
if (_tbIrqNextCycle)
{
_tbIrqNextCycle = false;
TriggerInterrupt(2);
}
}
public void ExecutePhase()
{
_taUnderflow = false;
if (DelayedInterrupts)
{
CheckIrqs();
}
if (_taPrb6NegativeNextCycle)
{
_prb &= 0xBF;
_taPrb6NegativeNextCycle = false;
}
if (_tbPrb7NegativeNextCycle)
{
_prb &= 0x7F;
_tbPrb7NegativeNextCycle = false;
}
switch (_taState)
{
case TimerState.WaitThenCount:
_taState = TimerState.Count;
Ta_Idle();
break;
case TimerState.Stop:
Ta_Idle();
break;
case TimerState.LoadThenStop:
_taState = TimerState.Stop;
_ta = _latcha;
Ta_Idle();
break;
case TimerState.LoadThenCount:
_taState = TimerState.Count;
_ta = _latcha;
Ta_Idle();
break;
case TimerState.LoadThenWaitThenCount:
_taState = TimerState.WaitThenCount;
if (_ta == 1)
{
Ta_Interrupt();
_taUnderflow = true;
}
else
{
_ta = _latcha;
}
Ta_Idle();
break;
case TimerState.Count:
Ta_Count();
break;
case TimerState.CountThenStop:
_taState = TimerState.Stop;
Ta_Count();
break;
}
switch (_tbState)
{
case TimerState.WaitThenCount:
_tbState = TimerState.Count;
Tb_Idle();
break;
case TimerState.Stop:
Tb_Idle();
break;
case TimerState.LoadThenStop:
_tbState = TimerState.Stop;
_tb = _latchb;
Tb_Idle();
break;
case TimerState.LoadThenCount:
_tbState = TimerState.Count;
_tb = _latchb;
Tb_Idle();
break;
case TimerState.LoadThenWaitThenCount:
_tbState = TimerState.WaitThenCount;
if (_tb == 1)
{
Tb_Interrupt();
}
else
{
_tb = _latchb;
}
Tb_Idle();
break;
case TimerState.Count:
Tb_Count();
break;
case TimerState.CountThenStop:
_tbState = TimerState.Stop;
Tb_Count();
break;
}
CountTod();
if (!_todLatch)
{
_latch10Ths = _tod10Ths;
_latchSec = _todSec;
_latchMin = _todMin;
_latchHr = _todHr;
}
_flagInput = ReadFlag();
if (!_flagInput && _flagLatch)
{
TriggerInterrupt(16);
}
_flagLatch = _flagInput;
if (!DelayedInterrupts)
{
CheckIrqs();
}
if ((_cra & 0x02) != 0)
_ddra |= 0x40;
if ((_crb & 0x02) != 0)
_ddrb |= 0x80;
}
private void Ta_Count()
{
if (_taCntPhi2)
{
if (_ta <= 0 || --_ta == 0)
{
if (_taState != TimerState.Stop)
{
Ta_Interrupt();
}
_taUnderflow = true;
}
}
Ta_Idle();
}
private void Ta_Interrupt()
{
_ta = _latcha;
_taIrqNextCycle = true;
_icr |= 1;
if ((_cra & 0x08) != 0)
{
_cra &= 0xFE;
_newCra &= 0xFE;
_taState = TimerState.LoadThenStop;
}
else
{
_taState = TimerState.LoadThenCount;
}
if ((_cra & 0x02) != 0)
{
if ((_cra & 0x04) != 0)
{
_taPrb6NegativeNextCycle = true;
_prb |= 0x40;
}
else
{
_prb ^= 0x40;
}
_ddrb |= 0x40;
}
}
private void Ta_Idle()
{
if (_hasNewCra)
{
switch (_taState)
{
case TimerState.Stop:
case TimerState.LoadThenStop:
if ((_newCra & 0x01) != 0)
{
_taState = (_newCra & 0x10) != 0
? TimerState.LoadThenWaitThenCount
: TimerState.WaitThenCount;
}
else
{
if ((_newCra & 0x10) != 0)
{
_taState = TimerState.LoadThenStop;
}
}
break;
case TimerState.Count:
if ((_newCra & 0x01) != 0)
{
if ((_newCra & 0x10) != 0)
{
_taState = TimerState.LoadThenWaitThenCount;
}
}
else
{
_taState = (_newCra & 0x10) != 0
? TimerState.LoadThenStop
: TimerState.CountThenStop;
}
break;
case TimerState.LoadThenCount:
case TimerState.WaitThenCount:
if ((_newCra & 0x01) != 0)
{
if ((_newCra & 0x08) != 0)
{
_newCra &= 0xFE;
_taState = TimerState.Stop;
}
else if ((_newCra & 0x10) != 0)
{
_taState = TimerState.LoadThenWaitThenCount;
}
}
else
{
_taState = TimerState.Stop;
}
break;
}
_cra = _newCra & 0xEF;
_hasNewCra = false;
}
}
private void Tb_Count()
{
if (_tbCntPhi2 || (_tbCntTa && _taUnderflow))
{
if (_tb <= 0 || --_tb == 0)
{
if (_tbState != TimerState.Stop)
{
Tb_Interrupt();
}
}
}
Tb_Idle();
}
private void Tb_Interrupt()
{
_tb = _latchb;
_tbIrqNextCycle = true;
_icr |= 2;
if ((_crb & 0x08) != 0)
{
_crb &= 0xFE;
_newCrb &= 0xFE;
_tbState = TimerState.LoadThenStop;
}
else
{
_tbState = TimerState.LoadThenCount;
}
if ((_crb & 0x02) != 0)
{
if ((_crb & 0x04) != 0)
{
_tbPrb7NegativeNextCycle = true;
_prb |= 0x80;
}
else
{
_prb ^= 0x80;
}
}
}
private void Tb_Idle()
{
if (_hasNewCrb)
{
switch (_tbState)
{
case TimerState.Stop:
case TimerState.LoadThenStop:
if ((_newCrb & 0x01) != 0)
{
_tbState = (_newCrb & 0x10) != 0
? TimerState.LoadThenWaitThenCount
: TimerState.WaitThenCount;
}
else
{
if ((_newCrb & 0x10) != 0)
{
_tbState = TimerState.LoadThenStop;
}
}
break;
case TimerState.Count:
if ((_newCrb & 0x01) != 0)
{
if ((_newCrb & 0x10) != 0)
{
_tbState = TimerState.LoadThenWaitThenCount;
}
}
else
{
_tbState = (_newCrb & 0x10) != 0
? TimerState.LoadThenStop
: TimerState.CountThenStop;
}
break;
case TimerState.LoadThenCount:
case TimerState.WaitThenCount:
if ((_newCrb & 0x01) != 0)
{
if ((_newCrb & 0x08) != 0)
{
_newCrb &= 0xFE;
_tbState = TimerState.Stop;
}
else if ((_newCrb & 0x10) != 0)
{
_tbState = TimerState.LoadThenWaitThenCount;
}
}
else
{
_tbState = TimerState.Stop;
}
break;
}
_crb = _newCrb & 0xEF;
_hasNewCrb = false;
}
}
private void TriggerInterrupt(int bit)
{
_icr |= bit;
if ((_intMask & bit) == 0) return;
_icr |= 0x80;
}
public void SyncState(Serializer ser)
{
SaveState.SyncObject(ser, this);
}
}
}