public CPU(Screen screen, RAM ram, Keyboard keyboard)
{
this.screen = screen;
this.ram = ram;
this.keyboard = keyboard;
VX = new byte[VX_SIZE];
SubroutineStack = new Stack <ushort>((int)STACK_SIZE);
Randomizer = new Random();
instructions = Instructions.GetInstructions();
PC = RAM.ROM_OFFSET;
}
private void instruction_0x0_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Close the window
if (instruction.KK == 0x00)
{
screen.Window.Close();
}
// Clear the screen
if (instruction.KK == 0xE0)
{
screen.Clear();
return;
}
// Return from a subroutine
if (instruction.KK == 0xEE)
{
cpu.PC = cpu.SubroutineStack.Pop();
return;
}
}
static async void StartEmulating(CLIOptions options)
{
Keyboard keyboard = new Keyboard(options.KeyboardDelay);
Screen screen = new Screen(options.Scale);
RAM ram = new RAM();
ram.LoadROM(options.RomPath);
CPU cpu = new CPU(screen, ram, keyboard);
timer = new Timer(60);
timer.OnTick += () => cpu.TimerTick();
screen.OnResumed += () => timer.Restart();
UpdateTimerAsync();
while (screen.Window.IsOpen)
{
cpu.Tick();
screen.Render();
}
}
private void instruction_0xE_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Skip next instruction if key with the value of Vx is pressed.
if (instruction.KK == 0x9E)
{
byte key = cpu.VX[instruction.X];
if (keyboard.IsKeyPressed(key))
{
cpu.SkipInstruction();
}
return;
}
// Skip next instruction if key with the value of Vx is not pressed.
if (instruction.KK == 0xA1)
{
byte key = cpu.VX[instruction.X];
if (!keyboard.IsKeyPressed(key))
{
cpu.SkipInstruction();
}
return;
}
}
private void instruction_0x2_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Call subroutine at nnn
cpu.SubroutineStack.Push(cpu.PC);
cpu.PC = instruction.NNN;
}
private void instruction_0x1_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Jump to location nnn
cpu.PC = instruction.NNN;
}
private void instruction_0xF_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Set Vx = delay timer value.
if (instruction.KK == 0x07)
{
cpu.VX[instruction.X] = cpu.DelayTimer;
return;
}
// Wait for a key press, store the value of the key in Vx.
// I THINK I'VE FOUND A F*****G ERROR!!!!
if (instruction.KK == 0x0A)
{
/*
* bool pressedKey = false;
* while (!pressedKey)
* {
* for (byte key = 0; key <= 0xF; ++key)
* {
* pressedKey = keyboard.IsKeyPressed(key);
* if (pressedKey)
* {
* cpu.VX[instruction.X] = key;
* break;
* }
* }
* }*/
bool pressedKey = false;
for (byte key = 0; key <= 0xF; ++key)
{
pressedKey = keyboard.IsKeyPressed(key);
if (pressedKey)
{
cpu.VX[instruction.X] = key;
break;
}
}
if (!pressedKey)
{
cpu.PC -= 2;
}
return;
}
// Set delay timer = Vx.
if (instruction.KK == 0x15)
{
cpu.DelayTimer = cpu.VX[instruction.X];
return;
}
// Set sound timer = Vx.
if (instruction.KK == 0x18)
{
cpu.SoundTimer = cpu.VX[instruction.X];
return;
}
// Set I = I + Vx.
if (instruction.KK == 0x1E)
{
cpu.I += cpu.VX[instruction.X];
return;
}
// Set I = location of sprite for digit Vx.
if (instruction.KK == 0x29)
{
cpu.I = (ushort)(RAM.SPRITES_OFFSET + cpu.VX[instruction.X] * RAM.SPRITE_SIZE);
return;
}
// Store BCD representation of Vx in memory locations I, I+1, and I+2.
if (instruction.KK == 0x33)
{
byte number = cpu.VX[instruction.X];
byte hundredsDigit = (byte)(Math.Floor((double)number / 100) % 10);
byte tensDigit = (byte)(Math.Floor((double)number / 10) % 10);
byte onesDigit = (byte)(number % 10);
byte[] data = { hundredsDigit, tensDigit, onesDigit };
ram.LoadToMemory(data, cpu.I);
return;
}
// Store registers V0 through Vx in memory starting at location I.
if (instruction.KK == 0x55)
{
byte[] data = new byte[instruction.X + 1];
for (uint i = 0; i <= instruction.X; ++i)
{
data[i] = cpu.VX[i];
}
ram.LoadToMemory(data, cpu.I);
return;
}
// Read registers V0 through Vx from memory starting at location I.
if (instruction.KK == 0x65)
{
byte[] data = ram.Read(cpu.I, (uint)cpu.I + instruction.X);
for (uint i = 0; i < data.Length; ++i)
{
cpu.VX[i] = data[i];
}
return;
}
}
private void instruction_0xB_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Jump to location nnn + V0
cpu.PC = (ushort)(instruction.NNN + cpu.VX[0]);
}
private void instruction_0xA_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Set I = nnn
cpu.I = instruction.NNN;
}
private void instruction_0x8_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Set Vx = Vy
if (instruction.N == 0x0)
{
cpu.VX[instruction.X] = cpu.VX[instruction.Y];
return;
}
// Set Vx = Vx OR Vy.
if (instruction.N == 0x1)
{
cpu.VX[instruction.X] = (byte)(cpu.VX[instruction.X] | cpu.VX[instruction.Y]);
return;
}
// Set Vx = Vx AND Vy
if (instruction.N == 0x2)
{
cpu.VX[instruction.X] = (byte)(cpu.VX[instruction.X] & cpu.VX[instruction.Y]);
return;
}
// Set Vx = Vx XOR Vy.
if (instruction.N == 0x3)
{
cpu.VX[instruction.X] = (byte)(cpu.VX[instruction.X] ^ cpu.VX[instruction.Y]);
return;
}
// Set Vx = Vx + Vy, set VF = carry.
if (instruction.N == 0x4)
{
if (cpu.VX[instruction.X] + cpu.VX[instruction.Y] > 255)
{
cpu.VX[0xF] = 1;
}
else
{
cpu.VX[0xF] = 0;
}
cpu.VX[instruction.X] = (byte)(cpu.VX[instruction.X] + cpu.VX[instruction.Y]);
return;
}
// Set Vx = Vx - Vy, set VF = NOT borrow.
if (instruction.N == 0x5)
{
if (cpu.VX[instruction.X] > cpu.VX[instruction.Y])
{
cpu.VX[0xF] = 1;
}
else
{
cpu.VX[0xF] = 0;
}
cpu.VX[instruction.X] = (byte)(cpu.VX[instruction.X] - cpu.VX[instruction.Y]);
return;
}
// Set Vx = Vx SHR 1
if (instruction.N == 0x6)
{
if ((cpu.VX[instruction.X] & 0x1) == 0x1)
{
cpu.VX[0xF] = 1;
}
else
{
cpu.VX[0xF] = 0;
}
cpu.VX[instruction.X] = (byte)(cpu.VX[instruction.X] / 2);
return;
}
// Set Vx = Vy - Vx, set VF = NOT borrow.
if (instruction.N == 0x7)
{
if (cpu.VX[instruction.Y] > cpu.VX[instruction.X])
{
cpu.VX[0xF] = 1;
}
else
{
cpu.VX[0xF] = 0;
}
cpu.VX[instruction.X] = (byte)(cpu.VX[instruction.Y] - cpu.VX[instruction.X]);
return;
}
// Set Vx = Vx SHL 1.
if (instruction.N == 0xE)
{
if ((cpu.VX[instruction.X] & 0x80) == 0x80)
{
cpu.VX[0xF] = 1;
}
else
{
cpu.VX[0xF] = 0;
}
cpu.VX[instruction.X] = (byte)(cpu.VX[instruction.X] * 2);
return;
}
}
private void instruction_0x7_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Set Vx = Vx + kk
cpu.VX[instruction.X] = (byte)(cpu.VX[instruction.X] + instruction.KK);
}
private void instruction_0x6_handler(CPUInstruction instruction, CPU cpu, RAM ram, Screen screen, Keyboard keyboard)
{
// Set Vx = kk
cpu.VX[instruction.X] = instruction.KK;
}