6502/EightBitNet
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Isolate effecitive address usage away from "intermediate" usage

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Adrian Conlon committed 2026-05-11 13:59:46 +01:00
1 parent 71d7832e91
commit ad97013127
1 file changed
+57 -53
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MC6809/MC6809.cs
+57 -53
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@@ -351,6 +351,8 @@ namespace MC6809
public Register16 S { get; } = new();
private Register16 EA { get; } = new();
public ref byte DP => ref this.dp;
public ref byte CC => ref this.cc;
@@ -495,8 +497,8 @@ namespace MC6809
this.DP = 0;
this.CC = SetBit(this.CC, StatusBits.IF); // Disable IRQ
this.CC = SetBit(this.CC, StatusBits.FF); // Disable FIRQ
this.GetWordPaged(0xff, RESET_vector);
this.Jump(this.Intermediate);
this.GetPagedInto(0xff, RESET_vector, this.EA);
this.Jump(this.EA);
}
protected override void HandleINT()
@@ -506,8 +508,8 @@ namespace MC6809
this.RaiseBS();
this.SaveEntireRegisterState();
this.CC = SetBit(this.CC, StatusBits.IF); // Disable IRQ
this.GetWordPaged(0xff, IRQ_vector);
this.Jump(this.Intermediate);
this.GetPagedInto(0xff, IRQ_vector, this.EA);
this.Jump(this.EA);
}
private void HandleHALT()
@@ -524,8 +526,8 @@ namespace MC6809
this.SaveEntireRegisterState();
this.CC = SetBit(this.CC, StatusBits.IF); // Disable IRQ
this.CC = SetBit(this.CC, StatusBits.FF); // Disable FIRQ
this.GetWordPaged(0xff, NMI_vector);
this.Jump(this.Intermediate);
this.GetPagedInto(0xff, NMI_vector, this.EA);
this.Jump(this.EA);
}
private void HandleFIRQ()
@@ -536,8 +538,8 @@ namespace MC6809
this.SavePartialRegisterState();
this.CC = SetBit(this.CC, StatusBits.IF); // Disable IRQ
this.CC = SetBit(this.CC, StatusBits.FF); // Disable FIRQ
this.GetWordPaged(0xff, FIRQ_vector);
this.Jump(this.Intermediate);
this.GetPagedInto(0xff, FIRQ_vector, this.EA);
this.Jump(this.EA);
}
#endregion
@@ -602,25 +604,25 @@ namespace MC6809
private void RelativeByteAddress()
{
var offset = (sbyte)this.FetchByte();
this.Intermediate.Word = (ushort)(this.PC.Word + offset);
this.EA.Word = (ushort)(this.PC.Word + offset);
}
private void RelativeWordAddress()
{
this.FetchWord();
var offset = (short)this.Intermediate.Word;
this.Intermediate.Word = (ushort)(this.PC.Word + offset);
this.EA.Word = (ushort)(this.PC.Word + offset);
}
private void DirectAddress()
{
this.Intermediate.Assign(this.FetchByte(), this.DP);
this.EA.Assign(this.FetchByte(), this.DP);
this.SwallowRead();
}
private void ExtendedAddress()
{
this.FetchWord();
this.FetchInto(this.EA);
this.SwallowRead();
}
@@ -646,56 +648,56 @@ namespace MC6809
switch (type & (byte)Mask.Four)
{
case 0b0000: // ,R+
this.Intermediate.Assign(r);
this.EA.Assign(r);
r.Word++;
this.SwallowCurrent();
this.SwallowRead(2);
break;
case 0b0001: // ,R++
this.Intermediate.Assign(r);
this.EA.Assign(r);
r.Word += 2;
this.SwallowCurrent();
this.SwallowRead(3);
break;
case 0b0010: // ,-R
--r.Word;
this.Intermediate.Assign(r);
this.EA.Assign(r);
this.SwallowCurrent();
this.SwallowRead(2);
break;
case 0b0011: // ,--R
r.Word -= 2;
this.Intermediate.Assign(r);
this.EA.Assign(r);
this.SwallowCurrent();
this.SwallowRead(3);
break;
case 0b0100: // ,R
this.Intermediate.Assign(r);
this.EA.Assign(r);
this.SwallowCurrent();
break;
case 0b0101: // B,R
this.Intermediate.Word = (ushort)(r.Word + (sbyte)this.B);
this.EA.Word = (ushort)(r.Word + (sbyte)this.B);
this.SwallowCurrent();
this.SwallowRead();
break;
case 0b0110: // A,R
this.Intermediate.Word = (ushort)(r.Word + (sbyte)this.A);
this.EA.Word = (ushort)(r.Word + (sbyte)this.A);
this.SwallowCurrent();
this.SwallowRead();
break;
case 0b1000: // n,R (eight-bit)
this.FetchByte();
this.Intermediate.Word = (ushort)(r.Word + (sbyte)this.Bus.Data);
this.EA.Word = (ushort)(r.Word + (sbyte)this.Bus.Data);
this.SwallowRead();
break;
case 0b1001: // n,R (sixteen-bit)
this.FetchWord();
this.Intermediate.Word += r.Word;
this.FetchInto(this.EA);
this.EA.Word += r.Word;
this.SwallowCurrent();
this.SwallowRead(2);
break;
case 0b1011: // D,R
this.Intermediate.Word = (ushort)(r.Word + this.D.Word);
this.EA.Word = (ushort)(r.Word + this.D.Word);
this.SwallowCurrent(3);
this.SwallowRead(2);
break;
@@ -709,7 +711,7 @@ namespace MC6809
this.SwallowRead(3);
break;
case 0b1111: // [n]
this.FetchWord();
this.FetchInto(this.EA);
this.SwallowCurrent();
break;
default:
@@ -719,15 +721,15 @@ namespace MC6809
var indirect = type & (byte)Bits.Bit4;
if (indirect != 0)
{
var address = this.Intermediate;
this.GetWord(address);
this.LEA(this.Bus.Address);
this.GetInto(this.EA);
this.SwallowRead();
}
}
else
{
// EA = ,R + 5-bit offset
this.Intermediate.Word = (ushort)(r.Word + SignExtend(5, (byte)(type & (byte)Mask.Five)));
this.EA.Word = (ushort)(r.Word + SignExtend(5, (byte)(type & (byte)Mask.Five)));
this.SwallowCurrent();
this.SwallowRead();
}
@@ -738,19 +740,19 @@ namespace MC6809
private void DirectByte()
{
this.DirectAddress();
this.MemoryRead(this.Intermediate);
this.MemoryRead(this.EA);
}
private void IndexedByte()
{
this.IndexedAddress();
this.MemoryRead(this.Intermediate);
this.MemoryRead(this.EA);
}
private void ExtendedByte()
{
this.ExtendedAddress();
this.MemoryRead(this.Intermediate);
this.MemoryRead(this.EA);
}
private void ImmediateWord() => this.FetchWord();
@@ -758,19 +760,19 @@ namespace MC6809
private void DirectWord()
{
this.DirectAddress();
this.GetWord(this.Intermediate);
this.GetWord(this.EA);
}
private void IndexedWord()
{
this.IndexedAddress();
this.GetWord(this.Intermediate);
this.GetWord(this.EA);
}
private void ExtendedWord()
{
this.ExtendedAddress();
this.GetWord(this.Intermediate);
this.GetWord(this.EA);
}
#endregion
@@ -807,7 +809,7 @@ namespace MC6809
private void STA() => this.Store(this.A);
private void STB() => this.Store(this.B);
private void Store(byte data) => this.MemoryWrite(this.Intermediate, this.Through(data));
private void Store(byte data) => this.MemoryWrite(this.EA, this.Through(data));
private void STD() => this.Store(this.D);
private void STU() => this.Store(this.U);
@@ -815,7 +817,7 @@ namespace MC6809
private void STX() => this.Store(this.X);
private void STY() => this.Store(this.Y);
private void Store(Register16 data) => this.SetWord(this.Intermediate, this.Through(data));
private void Store(Register16 data) => this.SetWord(this.EA, this.Through(data));
#endregion
@@ -825,13 +827,13 @@ namespace MC6809
{
this.RelativeWordAddress();
this.SwallowRead(4);
this.Call(this.Intermediate);
this.Call(this.EA);
}
private void BSR()
{
this.SwallowRead(3);
this.Call(this.Intermediate);
this.Call(this.EA);
}
private void BRA() => this.BranchShort(true);
@@ -870,14 +872,14 @@ namespace MC6809
private void BranchShort(bool condition)
{
this.Branch(this.Intermediate, condition);
this.Branch(this.EA, condition);
this.SwallowRead();
}
private void BranchLong(bool condition)
{
this.SwallowRead();
if (this.Branch(this.Intermediate, condition))
if (this.Branch(this.EA, condition))
{
this.SwallowRead();
}
@@ -1174,7 +1176,7 @@ namespace MC6809
private void SwallowPop(Register16 stack) => _ = this.MemoryRead(stack);
private void SwallowEffectiveAddress() => _ = this.MemoryRead(this.Intermediate);
private void SwallowEffectiveAddress() => _ = this.MemoryRead(this.EA);
#endregion
@@ -1790,7 +1792,7 @@ namespace MC6809
this.SwallowEffectiveAddress();
var result = this.Clear();
this.SwallowEffectiveAddress();
this.MemoryWrite(this.Intermediate, result);
this.MemoryWrite(this.EA, result);
}
private byte Clear()
@@ -1911,13 +1913,13 @@ namespace MC6809
return result;
}
private void JMP() => this.Jump(this.Intermediate);
private void JMP() => this.Jump(this.EA);
private void JSR()
{
this.SwallowEffectiveAddress();
this.SwallowRead();
this.Call(this.Intermediate);
this.Call(this.EA);
}
private void LSRA() => this.A = this.LogicalShiftRight(this.A);
@@ -2073,8 +2075,8 @@ namespace MC6809
this.CC = SetBit(this.CC, StatusBits.IF); // Disable IRQ
this.CC = SetBit(this.CC, StatusBits.FF); // Disable FIRQ
this.SwallowRead();
this.GetWordPaged(0xff, SWI_vector);
this.Jump(this.Intermediate);
this.GetPagedInto(0xff, SWI_vector, this.EA);
this.Jump(this.EA);
this.SwallowRead();
}
@@ -2084,8 +2086,8 @@ namespace MC6809
this.SwallowRead();
this.SaveEntireRegisterState();
this.SwallowRead();
this.GetWordPaged(0xff, SWI2_vector);
this.Jump(this.Intermediate);
this.GetPagedInto(0xff, SWI2_vector, this.EA);
this.Jump(this.EA);
this.SwallowRead();
}
@@ -2095,8 +2097,8 @@ namespace MC6809
this.SwallowRead();
this.SaveEntireRegisterState();
this.SwallowRead();
this.GetWordPaged(0xff, SWI3_vector);
this.Jump(this.Intermediate);
this.GetPagedInto(0xff, SWI3_vector, this.EA);
this.Jump(this.EA);
this.SwallowRead();
}
@@ -2114,19 +2116,21 @@ namespace MC6809
private void LEAX()
{
this.X.Assign(this.Intermediate);
this.LEA(this.X);
this.CC = this.AdjustZero(this.X);
}
private void LEAY()
{
this.Y.Assign(this.Intermediate);
this.LEA(this.Y);
this.CC = this.AdjustZero(this.Y);
}
private void LEAS() => this.S.Assign(this.Intermediate);
private void LEAS() => this.LEA(this.S);
private void LEAU() => this.U.Assign(this.Intermediate);
private void LEAU() => this.LEA(this.U);
private void LEA(Register16 register) => register.Assign(this.EA);
private void ABX()
{