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Correct a couple of anomolies in 6809 core

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Adrian Conlon committed 2026-05-05 21:29:10 +01:00
1 parent d5b92b01c9
commit 95b801b72f
2 files changed
+21 -15
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MC6809/MC6809.UnitTest/SbcTests.cs
+4 -4
View File
@@ -36,7 +36,7 @@ namespace MC6809.UnitTest
Assert.AreEqual(0, this.cpu.Overflow);
Assert.AreNotEqual(0, this.cpu.Negative);
Assert.AreNotEqual(0, this.cpu.Carry);
Assert.AreEqual(4, this.cpu.Cycles);
Assert.AreEqual(2, this.cpu.Cycles);
}
// Test the subtraction with carry instruction.
@@ -75,7 +75,7 @@ namespace MC6809.UnitTest
Assert.AreEqual(0, this.cpu.Overflow);
Assert.AreNotEqual(0, this.cpu.Zero);
Assert.AreEqual(0, this.cpu.Negative);
Assert.AreEqual(4, this.cpu.Cycles);
Assert.AreEqual(2, this.cpu.Cycles);
}
// Test the SBCA instruction.
@@ -93,7 +93,7 @@ namespace MC6809.UnitTest
Assert.AreEqual(0, this.cpu.Overflow);
Assert.AreEqual(0, this.cpu.Zero);
Assert.AreEqual(0, this.cpu.Negative);
Assert.AreEqual(4, this.cpu.Cycles);
Assert.AreEqual(2, this.cpu.Cycles);
}
// Test the SBCA instruction.
@@ -110,7 +110,7 @@ namespace MC6809.UnitTest
Assert.AreEqual(0, this.cpu.Overflow);
Assert.AreEqual(0, this.cpu.Zero);
Assert.AreNotEqual(0, this.cpu.Negative);
Assert.AreEqual(4, this.cpu.Cycles);
Assert.AreEqual(2, this.cpu.Cycles);
}
}
}
MC6809/MC6809.cs
+17 -11
View File
@@ -815,7 +815,7 @@ namespace MC6809
this.CC = this.AdjustNZ(data);
}
private void STA() => this.Store(this.B);
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));
@@ -1349,7 +1349,7 @@ namespace MC6809
case 0x73: this.Tick(7); this.ExtendedByte(); this.COM(); break; // COM (extended)
// CWAI
case 0x3c: this.Tick(11); this.DirectByte(); this.CWAI(); break; // CWAI (direct)
case 0x3c: this.Tick(11); this.ImmediateByte(); this.CWAI(); break; // CWAI (direct)
// DAA
case 0x19: this.Tick(2); this.DAA(); break; // DAA (inherent)
@@ -1501,13 +1501,13 @@ namespace MC6809
// SBC
// SBCA
case 0x82: this.Tick(4); this.ImmediateByte(); this.SBCA(); break; // SBC (SBCA immediate)
case 0x82: this.Tick(2); this.ImmediateByte(); this.SBCA(); break; // SBC (SBCA immediate)
case 0x92: this.Tick(4); this.DirectByte(); this.SBCA(); break; // SBC (SBCA direct)
case 0xa2: this.Tick(4); this.IndexedByte(); this.SBCA(); break; // SBC (SBCA indexed)
case 0xb2: this.Tick(5); this.ExtendedByte(); this.SBCA(); break; // SBC (SBCB extended)
// SBCB
case 0xc2: this.Tick(4); this.ImmediateByte(); this.SBCB(); break; // SBC (SBCB immediate)
case 0xc2: this.Tick(2); this.ImmediateByte(); this.SBCB(); break; // SBC (SBCB immediate)
case 0xd2: this.Tick(4); this.DirectByte(); this.SBCB(); break; // SBC (SBCB direct)
case 0xe2: this.Tick(4); this.IndexedByte(); this.SBCB(); break; // SBC (SBCB indexed)
case 0xf2: this.Tick(5); this.ExtendedByte(); this.SBCB(); break; // SBC (SBCB extended)
@@ -1811,24 +1811,30 @@ namespace MC6809
private void DAA()
{
var adjusted = this.A;
var original = this.A;
this.CC = SetBit(this.CC, StatusBits.CF, adjusted > 0x99);
var lowNibble = LowNibble(original);
var lowAdjust = this.HalfCarry != 0 || lowNibble > 9;
var lowAdjust = this.HalfCarry != 0 || LowNibble(adjusted) > 9;
var highAdjust = this.Carry != 0 || adjusted > 0x99;
var highNibble = HighNibble(original);
var highAdjust = this.Carry != 0 || highNibble > 9 || (highNibble == 9 && lowNibble > 9);
byte correction = 0;
if (lowAdjust)
{
adjusted += 6;
correction |= 0x06;
}
if (highAdjust)
{
adjusted += 0x60;
correction |= 0x60;
}
this.A = this.Through(adjusted);
var result = (byte)(original + correction);
var newCarry = (correction & 0x60) != 0;
this.A = this.Through(result);
this.CC = SetBit(this.CC, StatusBits.CF, newCarry);
}
private void EORA() => this.A = this.ExclusiveOr(this.A, this.Bus.Data);