public void update(MMU mmu)
{
byte JOYP = mmu.JOYP;
if (!isBit(4, JOYP))
{
mmu.JOYP = (byte)((JOYP & 0xF0) | pad);
if (pad != 0xF)
{
mmu.requestInterrupt(JOYPAD_INTERRUPT);
}
}
if (!isBit(5, JOYP))
{
mmu.JOYP = (byte)((JOYP & 0xF0) | buttons);
if (buttons != 0xF)
{
mmu.requestInterrupt(JOYPAD_INTERRUPT);
}
}
if ((JOYP & 0b00110000) == 0b00110000)
{
mmu.JOYP = 0xFF;
}
}
private void changeSTATMode(int mode, MMU mmu)
{
byte STAT = (byte)(mmu.STAT & ~0x3);
mmu.STAT = (byte)(STAT | mode);
//Accessing OAM - Mode 2 (80 cycles)
if (mode == 2 && isBit(5, STAT))
{ // Bit 5 - Mode 2 OAM Interrupt (1=Enable) (Read/Write)
mmu.requestInterrupt(LCD_INTERRUPT);
}
//case 3: //Accessing VRAM - Mode 3 (172 cycles) Total M2+M3 = 252 Cycles
//HBLANK - Mode 0 (204 cycles) Total M2+M3+M0 = 456 Cycles
else if (mode == 0 && isBit(3, STAT))
{ // Bit 3 - Mode 0 H-Blank Interrupt (1=Enable) (Read/Write)
mmu.requestInterrupt(LCD_INTERRUPT);
}
//VBLANK - Mode 1 (4560 cycles - 10 lines)
else if (mode == 1 && isBit(4, STAT))
{ // Bit 4 - Mode 1 V-Blank Interrupt (1=Enable) (Read/Write)
mmu.requestInterrupt(LCD_INTERRUPT);
}
}
private void handleTimer(int cycles, MMU mmu)
{
if (mmu.TAC_ENABLED)
{
timerCounter += cycles;
while (timerCounter >= TAC_FREQ[mmu.TAC_FREQ])
{
mmu.TIMA++;
timerCounter -= TAC_FREQ[mmu.TAC_FREQ];
}
if (mmu.TIMA == 0xFF)
{
mmu.requestInterrupt(TIMER_INTERRUPT);
mmu.TIMA = mmu.TMA;
}
}
}
public void update(int cycles, MMU mmu)
{
scanlineCounter += cycles;
byte currentMode = (byte)(mmu.STAT & 0x3); //Current Mode Mask
if (isLCDEnabled(mmu.LCDC))
{
switch (currentMode)
{
case 2: //Accessing OAM - Mode 2 (80 cycles)
if (scanlineCounter >= OAM_CYCLES)
{
changeSTATMode(3, mmu);
scanlineCounter -= OAM_CYCLES;
}
break;
case 3: //Accessing VRAM - Mode 3 (172 cycles) Total M2+M3 = 252 Cycles
if (scanlineCounter >= VRAM_CYCLES)
{
changeSTATMode(0, mmu);
drawScanLine(mmu);
scanlineCounter -= VRAM_CYCLES;
}
break;
case 0: //HBLANK - Mode 0 (204 cycles) Total M2+M3+M0 = 456 Cycles
if (scanlineCounter >= HBLANK_CYCLES)
{
mmu.LY++;
scanlineCounter -= HBLANK_CYCLES;
if (mmu.LY == SCREEN_HEIGHT)
{ //check if we arrived Vblank
changeSTATMode(1, mmu);
mmu.requestInterrupt(VBLANK_INTERRUPT);
RenderFrame();
}
else
{ //not arrived yet so return to 2
changeSTATMode(2, mmu);
}
}
break;
case 1: //VBLANK - Mode 1 (4560 cycles - 10 lines)
if (scanlineCounter >= SCANLINE_CYCLES)
{
mmu.LY++;
scanlineCounter -= SCANLINE_CYCLES;
if (mmu.LY > SCREEN_VBLANK_HEIGHT)
{ //check end of VBLANK
changeSTATMode(2, mmu);
mmu.LY = 0;
}
}
break;
}
if (mmu.LY == mmu.LYC)
{ //handle coincidence Flag
mmu.STAT = bitSet(2, mmu.STAT);
if (isBit(6, mmu.STAT))
{
mmu.requestInterrupt(LCD_INTERRUPT);
}
}
else
{
mmu.STAT = bitClear(2, mmu.STAT);
}
}
else
{ //LCD Disabled
scanlineCounter = 0;
mmu.LY = 0;
mmu.STAT = (byte)(mmu.STAT & ~0x3);
}
}