//Method: Fetch
//Purpose: Reads next word to execute, increments program counter.
public uint Fetch()
{
//retrive command pointed to by addr stored in register 15
uint command = myRegisters.ReadWord(15);
return(myMemory.ReadWord(command - 8));
//read word from RAM address specified by program counter register
//(program counter register is 15)
}
public uint getValue()
{
if (Instructions.getSectionValue(25, 25, instruction) == 1)
{
if (Instructions.getSectionValue(11, 8, instruction) == 0)
{
In_DataProcessing.opTwoDissasembly = '#' + Convert.ToString(Instructions.getSectionValue(7, 0, instruction));
}
type = 3;
In_DataProcessing.opTwoDissasembly = '#' + Convert.ToString((Instructions.getSectionValue(7, 0, instruction) >> (int)(2 * Instructions.getSectionValue(11, 8, instruction))) | (Instructions.getSectionValue(7, 0, instruction) << (32 - (int)(2 * Instructions.getSectionValue(11, 8, instruction)))));
return((Instructions.getSectionValue(7, 0, instruction) >> (int)(2 * Instructions.getSectionValue(11, 8, instruction))) | (Instructions.getSectionValue(7, 0, instruction) << (32 - (int)(2 * Instructions.getSectionValue(11, 8, instruction)))));
}
rm = Instructions.getSectionValue(3, 0, instruction);
shift = Instructions.getSectionValue(6, 5, instruction);
//this instruction will be shifting rn by something
if (rm == 15)
{
In_DataProcessing.opTwoDissasembly = "pc";
}
else
{
In_DataProcessing.opTwoDissasembly = 'r' + Convert.ToString(rm);
}
if (Instructions.getSectionValue(4, 4, instruction) == 1)
{
type = 2;
shiftAmt = myRegisters.ReadWord(Instructions.getSectionValue(11, 8, instruction));
strShiftAmt = 'r' + Convert.ToString(Instructions.getSectionValue(11, 8, instruction));
return(getShiftDone()); //calculate shift
}
else
{
type = 1;
shiftAmt = Instructions.getSectionValue(11, 7, instruction);
strShiftAmt = '#' + Convert.ToString(Instructions.getSectionValue(11, 7, instruction));
return(getShiftDone()); //calculate shift
}
}
public override void execute()
{
//switch statement to determine WHICH execute command to do.
switch (opcode)
{
case 1:
//to string
disassembly = "bx" + Instructions.firstOpcode + (myRegister.ReadWord(getSectionValue(3, 0, instruction)));
if (!disassembling)
{
executeBX();
}
break;
case 10:
//to string
disassembly = "b" + Instructions.firstOpcode + " " + (myRegister.ReadWord(15) + targetAddr);
if (!disassembling)
{
executeB();
}
break;
case 11:
//to string
disassembly = "bl" + Instructions.firstOpcode + " " + (myRegister.ReadWord(15) + targetAddr);
if (!disassembling)
{
executeBL();
}
break;
default:
break;
}
}
public uint getShiftDone()
{
rm = myRegisters.ReadWord(rm);
switch (shift)
{
case 0:
//LSL
if (shiftAmt != 0)
{
In_LoadStore.opTwoDissasembly += ", lsl " + strShiftAmt;
}
return(rm << (int)shiftAmt);
case 1:
//LSR
if (shiftAmt != 0)
{
In_LoadStore.opTwoDissasembly += ", lsr " + strShiftAmt;
}
return(rm >> (int)shiftAmt);
case 2:
//ASR
//CAST TO INT (logic shift becomes arithmaic)
if (shiftAmt != 0)
{
In_LoadStore.opTwoDissasembly += ", asr " + strShiftAmt;
}
return((uint)((int)rm >> (int)shiftAmt));
default:
//ROR
In_LoadStore.opTwoDissasembly += ", ror " + strShiftAmt;
return((rm >> (int)shiftAmt) | (rm << (int)(32 - shiftAmt)));
}
}
//Method: Run
//Purpose: Runs through entire simulated program using CPU fetch-decode-execute.
public void Run()
{
uint curCommand = myCPU.Fetch();
while (curCommand != 0 && !abort)
{
storedBranchPC = 0;
stepNum++;
//used for debugging stuffs
//check stepnum OR pc counter
/* if (stepNum == 2396)
* {
* string x;
* }*/
if (myCPU.Decode(curCommand))
{
if (Instructions.dontDoItBro == false)
{
myCPU.Execute();
//check to see if we wrote word to 100000
if (myRam.output)
{
//prompt user for input
//call event handler to update screen
if (outputQ.Count == 0)
{
output = '0';
}
else
{
output = outputQ.Dequeue();
}
myRam.output = false;
putChar(this, e);
}
}
else
{
myRegisters.IncrCounter();
}
curCommand = myCPU.Fetch();
if (trace)
{
if (storedBranchPC == 0)
{
WriteTrace((int)myRegisters.ReadWord(15) - 12);
}
else
{
WriteTrace(storedBranchPC);
}
}
}
else
{
if (trace)
{
WriteTrace((int)myRegisters.ReadWord(15) - 8);
}
curCommand = 0;
}
}
endRun(this, e);
}
public void executeMUL()
{
myRegister.WriteWord(rd, (myRegister.ReadWord(rs) * myRegister.ReadWord(rm)));
}
public void executeLDR()
{
int operand2int = Convert.ToInt32(operand2);
if (u == 0)
{
operand2int *= -1;
}
//gettin rn
if (p == 1)
{
addr = (uint)(myRegister.ReadWord(rn) + operand2int);
}
else if (p == 0)
{
addr = myRegister.ReadWord(rn);
}
//performing the load
if (bs == 0)
{
if (!disassembling)
{
myRegister.WriteWord(rd, myMemory.ReadWord(addr));
}
disassembly = "ldr" + Instructions.firstOpcode + " ";
}
else if (bs == 1)
{
if (!disassembling)
{
myRegister.WriteWord(rd, myMemory.ReadByte(addr));
}
disassembly = "ldrb" + Instructions.firstOpcode + " ";
}
disassembly += "r" + Convert.ToString(rd);
//writeback?
if (p == 1 && w == 1)
{
if (!disassembling)
{
myRegister.WriteWord(rn, addr);
}
disassembly += "!";
}
disassembly += ", [r" + Convert.ToString(rn) + opTwoDissasembly + "]";
}
public void executeADD()
{
myRegister.WriteWord(rd, (myRegister.ReadWord(rn) + operand2));
}