/// <summary>
/// Get the opcode.
/// </summary>
/// <param name="inputBits">instruction bits</param>
/// <returns>Operation</returns>
public Operation DecodeOpcode(int inputBits)
{
// Get mask for opcode + InstructionID
opcode = inputBits & BitUtilities.CreateBitMask(opcodeStartBit, 15);
switch (opcode)
{
case (int)opcodeIdentificationHexLiterals.hexADD:
return(new ADDoperation());
case (int)opcodeIdentificationHexLiterals.hexADC:
return(new ADCoperation());
case (int)opcodeIdentificationHexLiterals.hexSUB:
return(new SUBoperation());
case (int)opcodeIdentificationHexLiterals.hexMUL:
return(new MULoperation());
case (int)opcodeIdentificationHexLiterals.hexDIV:
return(new DIVoperation());
case (int)opcodeIdentificationHexLiterals.hexMOD:
return(new MODoperation());
case (int)opcodeIdentificationHexLiterals.hexAND:
return(new ANDoperation());
case (int)opcodeIdentificationHexLiterals.hexOR:
return(new ORoperation());
case (int)opcodeIdentificationHexLiterals.hexNOT:
return(new NOToperation());
case (int)opcodeIdentificationHexLiterals.hexNAND:
return(new NANDoperation());
case (int)opcodeIdentificationHexLiterals.hexJMP:
return(new JMPoperation());
case (int)opcodeIdentificationHexLiterals.hexJC:
return(new JCoperation());
case (int)opcodeIdentificationHexLiterals.hexCMP:
return(new CMPoperation());
case (int)opcodeIdentificationHexLiterals.hexNOP:
return(new NOPoperation());
case (int)opcodeIdentificationHexLiterals.hexLOAD:
return(new LOADoperation());
case (int)opcodeIdentificationHexLiterals.hexSTOR:
return(new STORoperation());
default:
throw new System.Exception("Invalid Opcode.");
}
}
private void DecodeFirstOperand(int inputBits)
{
operandOneValue = inputBits & BitUtilities.CreateBitMask(operandOneStartBit, operandOneEndBit);
if (operandOneValue < 0 || operandOneValue > 15)
{
operandTwoMeaning = $"OP1: Ya fucke* up";
}
else
{
operandOneMeaning = $"r{operandOneValue}";
}
}
private void DecodeSecondOperand(int inputBits)
{
operandTwoValue = inputBits & BitUtilities.CreateBitMask(operandTwoStartBit, operandTwoEndBit);
// Immediate or Register?
if (immediateSwitchValue == 0) // if register
{
if (operandTwoValue < 0 || operandTwoValue > 15)
{
operandTwoMeaning = $"OP2: Ya fucke* up";
}
operandTwoMeaning = $"r{operandTwoValue}";
}
else // else is an immediate
{
operandTwoMeaning = $"#{operandTwoValue}";
}
}
private void DecodeSecondOperand(int inputBits)
{
// Immediate or Register?
if (immediateSwitchValue == (int)ImmediateSwitchEnum.immediate) // This is an immediate value.
{
operandTwoValue = inputBits & BitUtilities.CreateBitMask(immediateOperandStartBit, operandTwoEndBit);
operandTwoMeaning = $"#{operandTwoValue}";
}
else
{
operandTwoValue = inputBits & BitUtilities.CreateBitMask(operandTwoStartBit, operandTwoEndBit);
if (operandTwoValue < 0 || operandTwoValue > 15)
{
operandTwoMeaning = $"OP2: Ya fucke* up";
}
operandTwoMeaning = $"r{operandTwoValue}";
}
}
/// <summary>
/// Decode value of the immediateSwitch
/// </summary>
/// <param name="inputBits">our instruction</param>
private void DecodeImmediateSwitch(int inputBits)
{
immediateSwitchValue = inputBits & BitUtilities.CreateBitMask(immediateSwitchStartBit, immediateSwitchEndBit);
}
