private static byte BitwiseSubstract(byte b1, byte b2)
{
//calculate two's complement
b2 = (byte)(~b2 + 1);
//calculate result
byte result = (byte)(b1 + b2);
//FLAGS
//set Carry flag if byte overflows OR if either b1 or b2 is zero
if (result < b1 || result < b2 || b1 == 0 || b2 == 0)
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.C, true);
}
else
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.C, false);
}
//set DC flag if 4th low order bit overflows OR if either b1 or b2 is zero
if (((((b1 & 15) + (b2 & 15)) & 16) == 16) || b1 == 0 || b2 == 0)
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.DC, true);
}
else
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.DC, false);
}
//set Z flag if result is zero
CheckZFlag(result);
return(result);
}
public static void RETFIE(Data.Command com)
{
Data.SetPC(Data.PopStack());
Data.SetPCLfromPC();
Data.SetRegisterBit(Data.Registers.INTCON, Data.Flags.Intcon.GIE, true); //Re-enable Global-Interrupt-Bit
SkipCycle();
}
/// <summary>
/// Bitwise add of two bytes, also sets Z, C and DC flag
/// </summary>
/// <param name="b1"></param>
/// <param name="b2"></param>
/// <returns></returns>
private static byte BitwiseAdd(byte b1, byte b2)
{
//calculate result
byte result = (byte)(b1 + b2);
//FLAGS
//set Carry flag if byte overflows
if (result < b1 || result < b2)
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.C, true);
}
else
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.C, false);
}
//set DC flag if 4th low order bit overflows
//if (((b1 & 8) == 8 || (b2 & 8) == 8) && (result & 8) == 0)
if ((((b1 & 15) + (b2 & 15)) & 16) == 16)
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.DC, true);
}
else
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.DC, false);
}
//set Z flag if result is zero
CheckZFlag(result);
return(result);
}
public static void CLRF(Data.Command com)
{
byte f = (byte)(com.GetLowByte() & 127);
Data.SetRegister(Data.AddressResolution(f), 0);
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.Z, true);
}
public static void RRF(Data.Command com)
{
byte d = (byte)(com.GetLowByte() & 128);
byte f = (byte)(com.GetLowByte() & 127);
byte result = (byte)(Data.GetRegister(Data.AddressResolution(f)) >> 1);
//Add carry bit if flag is set
if (Data.GetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.C))
{
result += 128;
}
//Set carry flag for current calculation
if ((Data.GetRegister(Data.AddressResolution(f)) & 1) == 1)
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.C, true);
}
else
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.C, false);
}
DirectionalWrite(d, f, result);
}
public static void SLEEP(Data.Command com)
{
CLRWDT(null);
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.TO, true);
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.PD, false);
Data.SetSleeping(true);
Data.SetPC(Data.GetPC() - 1);
}
public static void BSF(Data.Command com)
{
int b1 = (com.GetHighByte() & 3) << 1;
int b = b1 + (((com.GetLowByte() & 128) == 128) ? 1 : 0);
byte f = (byte)(com.GetLowByte() & 127);
Data.SetRegisterBit(Data.AddressResolution(f), b, true);
}
public static void CLRWDT(Data.Command com)
{
Data.ResetWatchdog();
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.TO, true);
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.PD, false);
if (Data.GetRegisterBit(Data.Registers.OPTION, Data.Flags.Option.PSA) == true)
{
Data.ResetPrePostScaler(); //Reset Postscaler if assigned to WDT
}
}
/// <summary>
/// sets Z flag to 1 if result is zero
/// </summary>
/// <param name="result"></param>
private static void CheckZFlag(byte result)
{
if (result == 0)
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.Z, true);
}
else
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.Z, false);
}
}
private static void CallInterrupt()
{
Data.PushStack();
Data.SetPC(0x04); //Fixed interrupt routine address
Data.SetRegisterBit(Data.Registers.INTCON, Data.Flags.Intcon.GIE, false); //Disable Global-Interrupt-Bit
if (Data.IsSleeping())
{
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.TO, true);
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.PD, false);
Data.IncPC();
Data.SetSleeping(false);
}
}
public static void CLRW(Data.Command com)
{
Data.SetRegisterW(0);
Data.SetRegisterBit(Data.Registers.STATUS, Data.Flags.Status.Z, true);
}