/// <summary>
/// Creates a new instance of the CPU with the given instruction memory.
/// </summary>
/// <param name="iMem">instruction memory, mapping memory location to instruction</param>
public Cpu(Dictionary<ushort, uint> iMem)
{
this.instructionMemory = new uint[0x400];
for (ushort i = 0; i < 0x400; i++)
{
if (iMem.ContainsKey(i))
instructionMemory[i] = iMem[i];
}
this.state = new CpuState();
this.SleepTickInterval = DefaultSleepTickInterval;
}
private void test(CpuState state, byte aVal, byte bVal)
{
state.ZeroFlag = (aVal & bVal) == 0;
//odd parity for C flag
var xor = aVal ^ bVal;
int count = 0;
int mask = 0x80;
while (mask != 0)
{
if ((mask & xor) != 0)
count++;
mask = mask >> 1;
}
state.CarryFlag = (count % 2) == 0;
}
private bool flowControlConditional(CpuState state, FlowControlCondition cond)
{
switch (cond)
{
case FlowControlCondition.Z:
return state.ZeroFlag;
case FlowControlCondition.NZ:
return !state.ZeroFlag;
case FlowControlCondition.C:
return state.CarryFlag;
case FlowControlCondition.NC:
return !state.CarryFlag;
default:
throw new NotSupportedException("Invalid flag.");
}
}
private void doShifter(CpuState state, byte reg, byte typeBits)
{
bool oldCarry;
ShifterOps type = (ShifterOps)typeBits;
byte val = state.RegisterFile[reg];
switch (type)
{
case ShifterOps.RL:
state.CarryFlag = (0x80 & val) != 0;
val = (byte)(val << 1);
if (state.CarryFlag)
val++;
break;
case ShifterOps.RR:
state.CarryFlag = (0x01 & val) == 1;
val = (byte)(val >> 1);
val |= (byte)(state.CarryFlag ? 0x80 : 0x0);
break;
case ShifterOps.SL0:
state.CarryFlag = (0x80 & val) != 0;
val = (byte)(val << 1);
break;
case ShifterOps.SL1:
state.CarryFlag = (0x80 & val) != 0;
val = (byte)(val << 1);
val |= 0x01;
break;
case ShifterOps.SLA:
oldCarry = state.CarryFlag;
state.CarryFlag = (0x80 & val) != 0;
val = (byte)(val << 1);
val |= (byte)(oldCarry ? 0x01 : 0x00);
break;
case ShifterOps.SLX:
bool oldBottomBit = (0x01 & val) == 1;
state.CarryFlag = (0x80 & val) != 0;
val = (byte)(val << 1);
val |= (byte)(oldBottomBit ? 0x01 : 0x00);
break;
case ShifterOps.SR0:
state.CarryFlag = (0x01 & val) != 0;
val = (byte)(val >> 1);
break;
case ShifterOps.SR1:
state.CarryFlag = (0x01 & val) != 0;
val = (byte)(val >> 1);
val |= 0x80;
break;
case ShifterOps.SRA:
oldCarry = state.CarryFlag;
state.CarryFlag = (0x01 & val) != 0;
val = (byte)(val >> 1);
val |= (byte)(oldCarry ? 0x80 : 0x00);
break;
case ShifterOps.SRX:
bool oldTopBit = (0x80 & val) == 1;
state.CarryFlag = (0x01 & val) != 0;
val = (byte)(val >> 1);
val |= (byte)(oldTopBit ? 0x80 : 0x00);
break;
default:
throw new NotSupportedException("Unsupported shifter operation.");
}
state.RegisterFile[reg] = val;
}
private byte doLogic(CpuState state, int value)
{
state.ZeroFlag = value == 0;
state.CarryFlag = false;
return (byte)value;
}
private void compare(CpuState state, byte aVal, byte bVal)
{
state.ZeroFlag = aVal == bVal;
state.CarryFlag = aVal < bVal;
}
private ushort call(CpuState state, ushort addr)
{
state.CallStack.Push(++state.ProgramCounter);
return addr;
}
private static byte sub(CpuState state, byte a, int b, bool cy)
{
int ret = a - b - (cy && state.CarryFlag ? 1 : 0);
state.CarryFlag = ret < 0;
state.ZeroFlag = (ret == 0) || (ret == -256);
return (byte)(0xFF & ret);
}
private static byte add(CpuState state, byte a, int b, bool cy)
{
int ret = a + b + (cy && state.CarryFlag ? 1 : 0);
state.CarryFlag = ret > 255;
state.ZeroFlag = (ret == 0) || ((ret + (state.CarryFlag ? 1 : 0)) == 256);
return (byte)(0xFF & ret);
}
/// <summary> /// Executes the operation on the given CPU state with the given arguments. /// </summary> /// <param name="state"></param> /// <param name="args"></param> public abstract void Do(CpuState state, ushort args);
/// <summary>
/// Stops and resets the processor.
/// </summary>
/// <returns>The the instructions per second executed.</returns>
public double Reset()
{
this.isRunning = false;
runThread.Join();
this.state = new CpuState();
foreach (var dev in devices)
{
hookupDevice(dev);
}
return tickCount / (endTime.Subtract(startTime).TotalSeconds);
}