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Tidy a couple of bits in the 6502 implementation

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This commit is contained in:
Adrian Conlon 2024-05-30 00:09:55 +01:00
parent a64f370d7c
commit 59098d0305
1 changed files with 19 additions and 19 deletions
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38
M6502/M6502.cs
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@ -730,15 +730,21 @@ namespace EightBit
}
// Addressing modes
// Addressing modes
private void NoteFixedAddress(Register16 fixing)
{
this.fixedPage = fixing.High;
this.Bus.Address.Low = fixing.Low;
}
private void NoteFixedAddress(int address)
{
this.NoteFixedAddress((ushort)address);
}
private void Address_Immediate() => this.Bus.Address.Word = this.PC.Word++;
private void NoteFixedAddress(ushort address)
{
this.intermediate.Word = address;
this.fixedPage = this.intermediate.High;
this.Bus.Address.Low = this.intermediate.Low;
}
private void Address_Immediate() => this.Bus.Address.Word = this.PC.Word++;
private void Address_Absolute() => this.Bus.Address.Word = this.FetchWord().Word;
@ -773,8 +779,7 @@ namespace EightBit
private void Address_AbsoluteWithIndex(byte index)
{
this.Address_Absolute();
this.intermediate.Word = (ushort)(this.Bus.Address.Word + index);
this.NoteFixedAddress(this.intermediate);
this.NoteFixedAddress(this.Bus.Address.Word + index);
}
private void Address_AbsoluteX() => this.Address_AbsoluteWithIndex(X);
@ -790,8 +795,7 @@ namespace EightBit
private void Address_IndirectIndexedY()
{
this.Address_ZeroPageIndirect();
this.intermediate.Word = (ushort)(this.Bus.Address.Word + Y);
this.NoteFixedAddress(this.intermediate);
this.NoteFixedAddress(this.Bus.Address.Word + Y);
}
// Addressing modes, with read
@ -869,8 +873,7 @@ namespace EightBit
{
var relative = (sbyte)this.Bus.Data;
this.Swallow();
this.intermediate.Word = (ushort)(this.PC.Word + relative);
this.NoteFixedAddress(this.intermediate);
this.NoteFixedAddress(this.PC.Word + relative);
this.Jump(this.intermediate.Word);
this.MaybeFixup();
}
@ -937,7 +940,6 @@ namespace EightBit
this.MemoryRead();
}
// Chew up a cycle
private void Swallow() => this.MemoryRead(this.PC);
@ -960,7 +962,7 @@ namespace EightBit
this.ResetFlag(StatusBits.CF, this.intermediate.High);
}
private byte SUB(byte operand, int borrow = 0) => this.Decimal != 0 ? SUB_d(operand, borrow) : SUB_b(operand, borrow);
private byte SUB(byte operand, int borrow) => this.Decimal != 0 ? SUB_d(operand, borrow) : SUB_b(operand, borrow);
private byte SUB_b(byte operand, int borrow = 0)
{
@ -971,10 +973,9 @@ namespace EightBit
private byte SUB_d(byte operand, int borrow)
{
_ = this.SUB_b(operand, borrow);
var data = this.Bus.Data;
this.intermediate.Word = (ushort)(operand - data - borrow);
var low = (byte)(LowNibble(operand) - LowNibble(data) - borrow);
var lowNegative = NegativeTest(low);
if (lowNegative != 0)
@ -992,7 +993,6 @@ namespace EightBit
return (byte)(PromoteNibble(high) | LowNibble(low));
}
private void ADC()
{
if (this.Decimal != 0)