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Rewrite 6502 interrupt handling

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This commit is contained in:
Adrian Conlon 2024-05-22 17:08:33 +01:00
parent f4ea6a0b13
commit 339af72d3b
1 changed files with 48 additions and 29 deletions
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77
M6502/M6502.cs
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@ -187,7 +187,7 @@ namespace EightBit
switch (this.OpCode)
{
case 0x00: this.FetchByte(); this.Interrupt(); break; // BRK (implied)
case 0x00: this.FetchByte(); this.Interrupt(IRQvector, InterruptSource.software); break; // BRK (implied)
case 0x01: this.A = this.OrR(this.A, this.AM_IndexedIndirectX()); break; // ORA (indexed indirect X)
case 0x02: break;
case 0x03: this.SLO(this.AM_IndexedIndirectX()); break; // *SLO (indexed indirect X)
@ -555,10 +555,18 @@ namespace EightBit
this.LowerRW();
base.OnRaisedPOWER();
}
protected override byte Pop()
{
this.RaiseStack();
return this.MemoryRead();
}
protected override byte Pop() => this.MemoryRead(++this.S, 1);
protected override void Push(byte value) => this.MemoryWrite(this.S--, 1, value);
protected override void Push(byte value)
{
this.LowerStack();
this.MemoryWrite(value);
}
protected virtual void RaiseSYNC()
{
@ -577,15 +585,13 @@ namespace EightBit
protected override sealed void HandleRESET()
{
this.RaiseRESET();
this.handlingRESET = true;
this.OpCode = 0x00; // BRK
this.Interrupt(RSTvector, InterruptSource.hardware, InterruptType.reset);
}
protected override sealed void HandleINT()
{
this.RaiseINT();
this.handlingINT = true;
this.OpCode = 0x00; // BRK
this.Interrupt(IRQvector);
}
protected override sealed void BusWrite()
@ -612,11 +618,15 @@ namespace EightBit
private static byte ClearBit(byte f, StatusBits flag, int condition) => ClearBit(f, (byte)flag, condition);
private void SetFlag(StatusBits flag)
{
this.P = SetBit(this.P, flag);
}
private void HandleNMI()
{
this.RaiseNMI();
this.handlingNMI = true;
this.OpCode = 0x00; // BRK
this.Interrupt(NMIvector);
}
private void HandleSO()
@ -625,37 +635,46 @@ namespace EightBit
this.P |= (byte)StatusBits.VF;
}
private void Interrupt()
enum InterruptSource { hardware, software };
enum InterruptType { reset, non_reset };
private void Interrupt(byte vector, InterruptSource source = InterruptSource.hardware, InterruptType type = InterruptType.non_reset)
{
var reset = this.handlingRESET;
var nmi = this.handlingNMI;
var irq = this.handlingINT;
var hardware = nmi || irq || reset;
var software = !hardware;
if (reset)
if (type == InterruptType.reset)
{
this.DummyPush(this.PC.High);
this.DummyPush(this.PC.Low);
this.DummyPush(this.P);
this.DummyPush();
this.DummyPush();
this.DummyPush();
}
else
{
this.PushWord(this.PC);
this.Push((byte)(this.P | (int)(software ? StatusBits.BF : 0)));
this.Push((byte)(this.P | (int)(source == InterruptSource.hardware ? 0 : StatusBits.BF)));
}
this.P = SetBit(this.P, StatusBits.IF); // Disable IRQ
var vector = reset ? RSTvector : (nmi ? NMIvector : IRQvector);
this.SetFlag(StatusBits.IF); // Disable IRQ
this.Jump(this.GetWordPaged(0xff, vector).Word);
this.handlingRESET = this.handlingNMI = this.handlingINT = false;
}
private void DummyPush(byte value)
private void UpdateStack(byte position)
{
this.Bus.Address.Word = new Register16(position, 1).Word;
}
private void LowerStack()
{
this.UpdateStack(this.S--);
}
private void RaiseStack()
{
this.UpdateStack(++this.S);
}
private void DummyPush()
{
this.LowerStack();
this.Tick();
this.Bus.Data = value;
this.Bus.Address.Low = this.S--;
this.Bus.Address.High = 1;
}
private Register16 Address_Absolute() => this.FetchWord();