private void PrintState()
{
Console.SetCursorPosition(0, 0);
string[] dumpLines = _ram.HexDump(0, 0x0800, 32).Split('\n', '\r');
dumpLines[0] += " Status Flags:";
dumpLines[1] += " N V U B D I Z C";
dumpLines[2] += String.Format(" {0} {1} {2} {3} {4} {5} {6} {7}",
_cpu.GetFlag(Flags.N) ? 1 : 0,
_cpu.GetFlag(Flags.V) ? 1 : 0,
_cpu.GetFlag(Flags.U) ? 1 : 0,
_cpu.GetFlag(Flags.B) ? 1 : 0,
_cpu.GetFlag(Flags.D) ? 1 : 0,
_cpu.GetFlag(Flags.I) ? 1 : 0,
_cpu.GetFlag(Flags.Z) ? 1 : 0,
_cpu.GetFlag(Flags.C) ? 1 : 0);
dumpLines[4] += String.Format(" A: ${0:X2}", _cpu.A);
dumpLines[5] += String.Format(" X: ${0:X2}", _cpu.X);
dumpLines[6] += String.Format(" Y: ${0:X2}", _cpu.Y);
dumpLines[7] += String.Format(" Stack P: ${0:X2}", _cpu.StackPointer);
dumpLines[8] += String.Format(" PC: ${0:X4}", _cpu.ProgramCounter);
//dumpLines[12] += String.Format(" Master Freq: {0}", _masterFps);
dumpLines[13] += String.Format(" Dots: {0}", _ppu.RemainingDotsInFrame);
Console.WriteLine();
Console.WriteLine(" Zeropage:");
foreach (string dumpLine in dumpLines)
{
Console.WriteLine(dumpLine);
}
}
public static byte ROR(I6502 cpu)
{
UInt16 shifted = cpu.Fetched;
// Add carry to bit 8 if set
if (cpu.GetFlag(Flags.C))
{
shifted |= 0x100;
}
// Update carry flag if bit 0 is 1.
cpu.SetFlag(Flags.C, (shifted & 0x01) == 0x01);
// Shift
shifted = (byte)(shifted >> 1);
UpdateZero(cpu, (byte)shifted);
UpdateNegative(cpu, shifted);
if (cpu.ImpliedAddress)
{
cpu.A = (byte)(shifted & 0x00FF);
}
else
{
cpu.Bus.Write(cpu.Address, (byte)shifted);
}
return(0);
}
public static byte ADC(I6502 cpu)
{
UInt16 sum = (UInt16)(cpu.A + cpu.Fetched + (cpu.GetFlag(Flags.C) ? 1 : 0));
UpdateCarry(cpu, sum);
UpdateZero(cpu, sum);
UpdateNegative(cpu, sum);
cpu.SetFlag(Flags.V, ((cpu.A ^ (byte)sum) & ~(cpu.A ^ cpu.Fetched) & 0x0080) == 0x0080);
cpu.A = (byte)(sum & 0x00FF);
return(1);
}
/**
* Mirror of OLC add Overflow truth table for subtraction
* A M ~A ~M R | V | A^M | A^R | ~M^R | M^R |
* --------------------------------------------
* 0 0 1 1 0 | 0 | 0 | 0 | 1 | 0
* 0 0 1 1 1 | 0 | 0 | 1 | 0 | 1
* 0 1 1 0 0 | 0 | 1 | 0 | 0 | 1
* 0 1 1 0 1 | 1 | 1 | 1 | 1 | 0
* 1 0 0 1 0 | 0 | 1 | 1 | 1 | 0
* 1 0 0 1 1 | 1 | 1 | 0 | 0 | 1
* 1 1 0 0 0 | 0 | 0 | 1 | 0 | 1
* 1 1 0 0 1 | 0 | 0 | 0 | 1 | 0
*/
public static byte SBC(I6502 cpu)
{
UInt16 inverse = (byte)~cpu.Fetched;
UInt16 difference = (UInt16)(cpu.A + inverse + (cpu.GetFlag(Flags.C) ? 1 : 0));
cpu.SetFlag(Flags.C, difference > 255);
cpu.SetFlag(Flags.Z, (difference & 0x00FF) == 0);
cpu.SetFlag(Flags.N, (difference & 0x0080) == 0x0080);
cpu.SetFlag(Flags.V, ((cpu.A ^ difference) & (cpu.A ^ cpu.Fetched) & 0x0080) == 0x0080);
cpu.A = (byte)(difference & 0x00FF);
return(1);
}
public static byte BCS(I6502 cpu)
{
byte extraCycles = 0;
if (cpu.GetFlag(Flags.C))
{
extraCycles++;
cpu.Address = (UInt16)(cpu.ProgramCounter + cpu.BranchRelativeAddress);
if ((cpu.Address & 0xFF00) != (cpu.ProgramCounter & 0xFF00))
{
extraCycles++;
}
cpu.ProgramCounter = cpu.Address;
}
return(extraCycles);
}
public static byte ROL(I6502 cpu)
{
UInt16 shifted = (UInt16)(cpu.Fetched << 1);
if (cpu.GetFlag(Flags.C))
{
shifted++;
}
UpdateCarry(cpu, shifted);
UpdateZero(cpu, (byte)shifted);
UpdateNegative(cpu, shifted);
if (cpu.ImpliedAddress)
{
cpu.A = (byte)(shifted & 0x00FF);
}
else
{
cpu.Bus.Write(cpu.Address, (byte)shifted);
}
return(0);
}
