public ExecutionResult Execute(Processor cpu, InstructionPackage package)
{
Instruction instruction = package.Instruction;
InstructionData data = package.Data;
Registers r = cpu.Registers;
Flags flags = cpu.Flags;
int result = 0x00 - r.A;
flags = FlagLookup.ByteArithmeticFlags(0x00, r.A, false, true);
flags.ParityOverflow = r.A == 0x80;
flags.Carry = r.A != 0x00;
r.A = (byte)result;
return(new ExecutionResult(package, flags));
}
public ExecutionResult Execute(Processor cpu, InstructionPackage package)
{
Instruction instruction = package.Instruction;
InstructionData data = package.Data;
Registers r = cpu.Registers;
byte offset = data.Argument1;
Flags flags = cpu.Flags;
if (instruction.TargetsWordRegister)
{
// inc 16-bit
WordRegister register = instruction.Target.AsWordRegister();
ushort value = r[register];
r[register] = (ushort)(value + 1);
}
else
{
byte value = 0;
if (instruction.TargetsByteInMemory)
{
// inc byte in memory
if (instruction.IsIndexed)
{
cpu.Timing.InternalOperationCycle(5);
}
value = instruction.MarshalSourceByte(data, cpu, out ushort address, out ByteRegister source);
cpu.Memory.Timed.WriteByteAt(address, (byte)(value + 1));
}
else
{
// it's an 8-bit inc
ByteRegister register = instruction.Target.AsByteRegister();
value = r[register];
r[register] = (byte)(value + 1);
}
bool carry = flags.Carry;
flags = FlagLookup.ByteArithmeticFlags(value, 1, false, false);
flags.ParityOverflow = (value == 0x7F);
flags.Carry = carry; // always unaffected
flags.Subtract = false;
}
return(new ExecutionResult(package, flags));
}
public static (byte Result, Flags Flags) Add(byte left, byte right, bool carry)
{
Flags flags = FlagLookup.ByteArithmeticFlags(left, right, carry, false);
return((byte)(left + right + (carry ? 1 : 0)), flags);
}
public static (byte Result, Flags Flags) Subtract(byte left, byte right, bool carry)
{
Flags flags = FlagLookup.ByteArithmeticFlags(left, right, carry, true);
return((byte)(left - right - (carry ? 1 : 0)), flags);
}
