public void decode()
{
/*************************** SPECIAL CASES ****************************/
// SWI CASE
if (Extras.isSWIInstruction(currentInstruction))
{
return;
}
// MUL CASE
if (Extras.isMulInstruction(currentInstruction))
{
mul_instruct = new Mul(memory, registers, currentInstruction, currentInstAddress);
mul_instruct.decodeMul();
return;
}
// BX CASE
if (Extras.isBX(currentInstruction))
{
bx_instruct = new Bx(memory, registers, currentInstruction, currentInstAddress);
bx_instruct.decodeBx();
return;
}
/*************************** NORMAL CASES ******************************/
// get instruction type
currentInstructionType = Extras.getNormalInstructionType(currentInstruction);
// NORMAL CASES: create an instruction according to its type
// and decode the instruction
switch (currentInstructionType)
{
case 0: // if Data Processing (00x)
case 1: // if Data Processing (00x)
data_processing_instruct = new DataProcessing(memory, registers, currentInstruction, currentInstAddress);
data_processing_instruct.decodeDP();
break;
case 2: // if Load/Store (01x)
case 3: // if Load/Store (01x)
load_store_instruct = new LoadAndStore(memory, registers, currentInstruction, currentInstAddress);
load_store_instruct.decodeLaS();
break;
case 4: // if Load/Store (100) Load/Store Multiple FD variant
load_store_mul_instruct = new LoadAndStoreMul(memory, registers, currentInstruction, currentInstAddress);
load_store_mul_instruct.decodeLaSMul();
break;
case 5: // if Branch (101)
branch_instruct = new Branch(memory, registers, currentInstruction, currentInstAddress);
branch_instruct.decodeB();
break;
default:
instDisLst.Add("Special Instruction");
Debug.WriteLine("ERROR in CPU.execute(): Type is Special or Non-valid instruction.");
Debug.WriteLine("ERROR in CPU.decode(): Type is Special or Non-valid instruction.");
break;
}
}