// CPI Compare Immediate With Accumulator
// The byte of immediate data is compared to the contents of the accumulator.
private int CPI(byte b)
{
var cmp16 = Accumulator - b;
Flags = Flags
.Set(FlagIndex.Carry, ((cmp16 & 0x00FF) >= Accumulator && b != 0))
.Set(FlagIndex.AuxCarry, AuxCarryPredicates.calc_subAC(Accumulator, b))
.calc_SZP((byte)cmp16);
return(7);
}
// Compare
private int CMP(IByteOperandStrategy operand)
{
var cmp16 = Accumulator - operand.Read(this);
Flags = Flags
.Set(FlagIndex.Carry, ((cmp16 & 0x00FF) >= Accumulator && operand.Read(this) != 0))
.Set(FlagIndex.AuxCarry, AuxCarryPredicates.calc_subAC(Accumulator, operand.Read(this)))
.calc_SZP((byte)cmp16);
return(operand == OpMem ? 7 : 4);
}
// DCR Decrement Register or Memory
// The specified register or memory byte is decremented by one.
// If the H register contains 3AH, the L register contains 7CH, and memory location 3A7CH contains 40H,
// the instruction: OCR M
// will cause memory location 3A7CH to contain 3FH.
private int DCR(IByteOperandStrategy op)
{
var in8 = op.Read(this);
var out8 = (byte)(in8 - 1);
Flags = Flags
.Set(FlagIndex.AuxCarry, AuxCarryPredicates.calc_subAC(in8, 1))
.calc_SZP(out8);
op.Write(this, out8);
return(op == OpMem ? 10 : 5);
}
//SUI Subtract Immediate From Accumulator
// The byte of immediate data is subtracted from the contents of the accumulator using two's complement arithmetic.
private int SUI(byte b)
{
var out16 = (ushort)(Accumulator - b);
Flags = Flags
.Set(FlagIndex.Carry, ((out16 & 0x00FF) >= Accumulator && b != 0))
.Set(FlagIndex.AuxCarry, AuxCarryPredicates.calc_subAC(Accumulator, b))
.calc_SZP((byte)out16);
Accumulator = (byte)out16;
return(7);
}
// SUB Subtract Register or Memory From Accumulator
private int SUB(IByteOperandStrategy operand)
{
var in8 = operand.Read(this);
var out16 = Accumulator - in8;
Flags = Flags
.Set(FlagIndex.Carry, ((out16 & 0x00FF) >= Accumulator && in8 != 0))
.Set(FlagIndex.AuxCarry, AuxCarryPredicates.calc_subAC(Accumulator, in8))
.calc_SZP((byte)out16);
Accumulator = (byte)out16;
return(operand == OpMem ? 7 : 4);
}
