public byte ReadByte(int address)
{
if (address < 0XFF)
{
return(_bios[address]);
}
if (address < 0x8000)
{
return(_cartridge.ReadByte(address));
}
if (address < 0xA000)
{
return(_gpu.ReadByte(address));
}
if (address < 0xC000)
{
return(_cartridge.ReadByte(address));
}
if (address < 0xFE00)
{
return(_lowRam[address]);
}
if (address < 0xFEA0)
{
return(_gpu.ReadByte(address));
}
if (address < 0xFF40)
{
return(_sound[address - 0xFF00]);
}
if (address < 0xFF80)
{
return(_gpu.ReadByte(address));
}
if (address < 0xFFFF) // FF80 -> FFFE
{
return(_highRam[address & 0x7F]);
}
return(GetBufferArea(address)[0]);
throw new NotImplementedException("MMU failed at address " + address);
}
public void WriteByteTest(ushort address, byte value, byte expected)
{
var data = new byte[0x8000];
_cartridge = new Cartridge(data);
_cartridge.WriteByte(address, value);
Assert.Equal(expected, _cartridge.ReadByte(address));
}
public void ReadByteTest(ushort address, byte expected)
{
var data = new byte[0x8000];
if (address < data.Length)
{
data[address] = expected;
}
_cartridge = new Cartridge(data);
Assert.Equal(expected, _cartridge.ReadByte(address));
}
// For debugging display
public string NextThreeBytes()
{
return(cartridge.ReadByte(PC).ToString("X2") + " " + cartridge.ReadByte((ushort)(PC + 1)).ToString("X2") + " " + cartridge.ReadByte((ushort)(PC + 2)).ToString("X2"));
}
public int ReadByte(int address)
{
if (address <= 0x7FFF || (address >= 0xA000 && address <= 0xBFFF))
{
return(cartridge.ReadByte(address));
}
else if (address >= 0x8000 && address <= 0x9FFF)
{
return(vRam[address - 0x8000]);
}
else if (address >= 0xC000 && address <= 0xDFFF)
{
return(wRam[address - 0xC000]);
}
else if (address >= 0xE000 && address <= 0xFDFF)
{
return(wRam[address - 0xE000]);
}
else if (address >= 0xFE00 && address <= 0xFEFF)
{
return(oam[address - 0xFE00]);
}
else if (address >= 0xFF80 && address <= 0xFFFE)
{
return(highRam[0xFF & address]);
}
else
{
switch (address)
{
case 0xFF00: // key pad
if (keyP14)
{
int value = 0;
if (!downKeyPressed)
{
value |= 0x08;
}
if (!upKeyPressed)
{
value |= 0x04;
}
if (!leftKeyPressed)
{
value |= 0x02;
}
if (!rightKeyPressed)
{
value |= 0x01;
}
return(value);
}
else if (keyP15)
{
int value = 0;
if (!startButtonPressed)
{
value |= 0x08;
}
if (!selectButtonPressed)
{
value |= 0x04;
}
if (!bButtonPressed)
{
value |= 0x02;
}
if (!aButtonPressed)
{
value |= 0x01;
}
return(value);
}
break;
case 0xFF04: // Timer divider
return(Z80.ticks & 0xFF);
case 0xFF05: // Timer counter
return(Z80.timerCounter & 0xFF);
case 0xFF06: // Timer modulo
return(Z80.timerModulo & 0xFF);
case 0xFF07:
{ // Time Control
int value = 0;
if (Z80.timerRunning)
{
value |= 0x04;
}
value |= (int)Z80.timerFrequency;
return(value);
}
case 0xFF0F:
{ // Interrupt Flag (an interrupt request)
int value = 0;
if (Z80.keyPressedInterruptRequested)
{
value |= 0x10;
}
if (Z80.serialIOTransferCompleteInterruptRequested)
{
value |= 0x08;
}
if (Z80.timerOverflowInterruptRequested)
{
value |= 0x04;
}
if (Z80.lcdcInterruptRequested)
{
value |= 0x02;
}
if (Z80.vBlankInterruptRequested)
{
value |= 0x01;
}
return(value);
}
case 0xFF40:
{ // LCDC control
int value = 0;
if (Z80.lcdControlOperationEnabled)
{
value |= 0x80;
}
if (GPU.windowTileMapDisplaySelect)
{
value |= 0x40;
}
if (GPU.windowDisplayed)
{
value |= 0x20;
}
if (GPU.backgroundAndWindowTileDataSelect)
{
value |= 0x10;
}
if (GPU.backgroundTileMapDisplaySelect)
{
value |= 0x08;
}
if (GPU.largeSprites)
{
value |= 0x04;
}
if (GPU.spritesDisplayed)
{
value |= 0x02;
}
if (GPU.backgroundDisplayed)
{
value |= 0x01;
}
return(value);
}
case 0xFF41:
{ // LCDC Status
int value = 0;
if (GPU.lcdcLycLyCoincidenceInterruptEnabled)
{
value |= 0x40;
}
if (GPU.lcdcOamInterruptEnabled)
{
value |= 0x20;
}
if (GPU.lcdcVBlankInterruptEnabled)
{
value |= 0x10;
}
if (GPU.lcdcHBlankInterruptEnabled)
{
value |= 0x08;
}
if (GPU.ly == GPU.lyCompare)
{
value |= 0x04;
}
value |= (int)GPU.lcdcMode;
return(value);
}
case 0xFF42: // Scroll Y
return(GPU.scrollY);
case 0xFF43: // Scroll X
return(GPU.scrollX);
case 0xFF44: // LY
return(GPU.ly);
case 0xFF45: // LY Compare
return(GPU.lyCompare);
case 0xFF47:
{ // Background palette
GPU.invalidateAllBackgroundTilesRequest = true;
int value = 0;
for (int i = 3; i >= 0; i--)
{
value <<= 2;
switch (GPU.backgroundPalette[i])
{
case 0xFF000000:
value |= 3;
break;
case 0xFF555555:
value |= 2;
break;
case 0xFFAAAAAA:
value |= 1;
break;
case 0xFFFFFFFF:
break;
}
}
return(value);
}
case 0xFF48:
{ // Object palette 0
GPU.invalidateAllSpriteTilesRequest = true;
int value = 0;
for (int i = 3; i >= 0; i--)
{
value <<= 2;
switch (GPU.objectPallete0[i])
{
case 0xFF000000:
value |= 3;
break;
case 0xFF555555:
value |= 2;
break;
case 0xFFAAAAAA:
value |= 1;
break;
case 0xFFFFFFFF:
break;
}
}
return(value);
}
case 0xFF49:
{ // Object palette 1
GPU.invalidateAllSpriteTilesRequest = true;
int value = 0;
for (int i = 3; i >= 0; i--)
{
value <<= 2;
switch (GPU.objectPallete1[i])
{
case 0xFF000000:
value |= 3;
break;
case 0xFF555555:
value |= 2;
break;
case 0xFFAAAAAA:
value |= 1;
break;
case 0xFFFFFFFF:
break;
}
}
return(value);
}
case 0xFF4A: // Window Y
return(GPU.windowY);
case 0xFF4B: // Window X
return(GPU.windowX);
case 0xFFFF:
{ // Interrupt Enable
int value = 0;
if (Z80.keyPressedInterruptEnabled)
{
value |= 0x10;
}
if (Z80.serialIOTransferCompleteInterruptEnabled)
{
value |= 0x08;
}
if (Z80.timerOverflowInterruptEnabled)
{
value |= 0x04;
}
if (Z80.lcdcInterruptEnabled)
{
value |= 0x02;
}
if (Z80.vBlankInterruptEnabled)
{
value |= 0x01;
}
return(value);
}
}
}
return(0);
}
public byte ReadByte(ushort addr)
{
if (addr < 0x8000)
{
if (RomMapMode == MapMode.Boot && addr < bootRom?.Length)
{
return(bootRom[addr]);
}
else
{
return(cartridge.ReadByte(addr));
}
}
else if (addr < 0xA000)
{
return(videoRam[addr - 0x8000]);
}
else if (addr < 0xC000)
{
return(cartridge.ReadByte(addr));
}
else if (addr < 0xE000)
{
return(workRam[addr - 0xC000]);
}
else if (addr < 0xFE00)
{
// Echo of internal RAM
return(workRam[addr - 0xE000]);
}
else if (addr < 0xFEA0)
{
return(oam[addr - 0xFE00]);
}
else if (addr < 0xFF00)
{
// Empty but unusable for I/O, return default bus value 0xFF
return(0xFF);
}
else if (addr < 0xFF4C)
{
ioMasks.TryGetValue(addr, out byte mask);
if (addr == 0xFF00)
{
ioRegisters[0] = inputRegister.ReadValue(ioRegisters[0]);
}
return((byte)(ioRegisters[addr - 0xFF00] | mask));
}
else if (addr < 0xFF80)
{
// Empty but unusable for I/O, return default bus value 0xFF
return(0xFF);
}
else if (addr < 0xFFFF)
{
return(highRam[addr - 0xFF80]);
}
else if (addr == 0xFFFF)
{
return(interruptEnableRegister);
}
else
{
throw new ArgumentException($"Could not read from illegal memory address: {addr:X4}");
}
}