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MC6809: fix DAA

This commit is contained in:
alyosha-tas 2019-07-10 19:30:17 -04:00
parent fd51934ea4
commit 5e2b097902
2 changed files with 45 additions and 32 deletions
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39
BizHawk.Emulation.Cores/CPUs/MC6800/Operations.cs
View File

@ -108,6 +108,7 @@ namespace BizHawk.Emulation.Common.Components.MC6800
FlagZ = Regs[src] == 0;
FlagV = false;
FlagN = (Regs[src] & 0xFF) > 127;
FlagC = false;
}
public void CLR_Func(ushort src)
@ -371,28 +372,34 @@ namespace BizHawk.Emulation.Common.Components.MC6800
Regs[dest] = ans;
}
// DA code courtesy of AWJ: http://forums.nesdev.com/viewtopic.php?f=20&t=15944
public void DA_Func(ushort src)
{
byte a = (byte)Regs[src];
int a = Regs[src];
if (!FlagN)
{ // after an addition, adjust if (half-)carry occurred or if result is out of bounds
if (FlagC || a > 0x99) { a += 0x60; FlagC = true; }
if (FlagH || (a & 0x0f) > 0x09) { a += 0x6; }
byte CF = 0;
if (FlagC || ((a & 0xF) > 9))
{
CF = 6;
}
if (FlagC || (((a >> 4) & 0xF) > 9) || ((((a >> 4) & 0xF) > 8) && ((a & 0xF) > 9)))
{
CF |= (byte)(6 << 4);
}
a += CF;
if ((a > 0xFF) || FlagC)
{
FlagC = true;
}
else
{ // after a subtraction, only adjust if (half-)carry occurred
if (FlagC) { a -= 0x60; }
if (FlagH) { a -= 0x6; }
{
FlagC = false;
}
a &= 0xFF;
Regs[src] = a;
FlagZ = a == 0;
FlagH = false;
Regs[src] = (byte)a;
FlagN = a > 127;
FlagZ = a == 0;
// FlagV is listed as undefined in the documentation
}
public void CMP16_Func(ushort dest, ushort src)

38
BizHawk.Emulation.Cores/CPUs/MC6809/Operations.cs
View File

@ -438,28 +438,34 @@ namespace BizHawk.Emulation.Common.Components.MC6809
Regs[dest] = ans;
}
// DA code courtesy of AWJ: http://forums.nesdev.com/viewtopic.php?f=20&t=15944
public void DA_Func(ushort src)
{
byte a = (byte)Regs[src];
int a = Regs[src];
if (!FlagN)
{ // after an addition, adjust if (half-)carry occurred or if result is out of bounds
if (FlagC || a > 0x99) { a += 0x60; FlagC = true; }
if (FlagH || (a & 0x0f) > 0x09) { a += 0x6; }
byte CF = 0;
if (FlagC || ((a & 0xF) > 9))
{
CF = 6;
}
if (FlagC || (((a >> 4) & 0xF) > 9) || ((((a >> 4) & 0xF) > 8) && ((a & 0xF) > 9)))
{
CF |= (byte)(6 << 4);
}
a += CF;
if ((a > 0xFF) || FlagC)
{
FlagC = true;
}
else
{ // after a subtraction, only adjust if (half-)carry occurred
if (FlagC) { a -= 0x60; }
if (FlagH) { a -= 0x6; }
{
FlagC = false;
}
a &= 0xFF;
Regs[src] = a;
FlagZ = a == 0;
FlagH = false;
Regs[src] = (byte)a;
FlagN = a > 127;
FlagZ = a == 0;
// FlagV is listed as undefined in the documentation
}
// D register implied