public void Step(int previousInstructionCycles)
{
ModeClock += previousInstructionCycles;
switch (Mode)
{
case GPUModes.HBlank:
if (ModeClock >= 204)
{
ModeClock = 0;
CurrentLine++;
if (CurrentLine == 143)
{
Mode = GPUModes.VBlank;
// WRITE TO THE SCREEN HERE
}
else
{
Mode = GPUModes.ScanlineOAMRead;
}
}
break;
case GPUModes.VBlank:
if (ModeClock >= 456)
{
ModeClock = 0;
CurrentLine++;
if (CurrentLine > 153)
{
Mode = GPUModes.ScanlineOAMRead;
CurrentLine = 0;
}
}
break;
case GPUModes.ScanlineOAMRead:
if (ModeClock >= 80)
{
ModeClock = 0;
Mode = GPUModes.ScanlineVRAMRead;
}
break;
case GPUModes.ScanlineVRAMRead:
if (ModeClock >= 172)
{
ModeClock = 0;
Mode = GPUModes.HBlank;
// WRITE THE SCANLINE HERE
}
break;
}
}
public void Reset()
{
modeClocks = 0;
scrollX = 0;
scrollY = 0;
winX = 0;
winY = 0;
line = 0;
mode = GPUModes.OAM_READ;
tileSet = new GPUTile[512];
for (var i = 0; i < 512; i++)
{
tileSet[i] = new GPUTile();
}
VRamBuffer = new Color[256 * 256];
for (var i = 0; i < 256 * 256; i++)
{
VRamBuffer[i] = Color.White;
}
oam = new byte[160];
switchLCD = true;
switchBg = false;
switchWin = false;
objSize = false;
objs = new GPUObject[40];
prioObjects = new GPUObject[40];
for (var i = 0; i < 40; i++)
{
objs[i] = new GPUObject {
Pos = i,
Y = -16,
X = -8,
Tile = 0,
Palette = 0,
YFlip = false,
XFlip = false
};
prioObjects[i] = objs[i];
}
switchObj = false;
lineCompare = 0;
lcdStat = 0;
interruptsFired = 0;
bgTileBase = 0x0000;
bgMapBase = 0x1800;
winMapBase = 0x1800;
}
public void Cycle()
{
// if (!switchLCD) return;
modeClocks += cpu.reg.lastClockM;
switch (mode)
{
case GPUModes.HBLANK:
if (modeClocks >= HorizontalBlankCycles)
{
modeClocks = 0;
line++;
if (line == 144)
{
mode = GPUModes.VBLANK;
cpu.reg.TriggerInterrupts |= Flags.INT_VBLANK;
if (FlagVBlankMode && cpu.reg.InterruptEnable)
{
cpu.reg.TriggerInterrupts |= Flags.INT_LCDSTAT;
}
}
else
{
mode = GPUModes.OAM_READ;
if (FlagOamMode && cpu.reg.InterruptEnable)
{
cpu.reg.TriggerInterrupts |= Flags.INT_LCDSTAT;
}
}
if (line == lineCompare && FlagLycLy && cpu.reg.InterruptEnable)
{
cpu.reg.TriggerInterrupts |= Flags.INT_LCDSTAT;
}
}
break;
case GPUModes.VBLANK:
if (modeClocks >= (VerticalBlankCycles / 9))
{
modeClocks = 0;
line++;
if (line == lineCompare && FlagLycLy)
{
cpu.reg.TriggerInterrupts |= Flags.INT_LCDSTAT;
}
if (line > 153)
{
mode = GPUModes.OAM_READ;
line = 0;
if (FlagOamMode && cpu.reg.InterruptEnable)
{
cpu.reg.TriggerInterrupts |= Flags.INT_LCDSTAT;
}
}
}
break;
case GPUModes.OAM_READ:
if (modeClocks >= OamCycles)
{
modeClocks = 0;
mode = GPUModes.VRAM_READ;
}
break;
case GPUModes.VRAM_READ:
if (modeClocks >= VRamCycles)
{
modeClocks = 0;
RenderScanline();
mode = GPUModes.HBLANK;
// TODO: DMA
if (FlagHBlankMode && cpu.reg.InterruptEnable)
{
cpu.reg.TriggerInterrupts |= Flags.INT_LCDSTAT;
}
}
break;
default:
Console.WriteLine($"BUG! Went to a unknown state: {mode}");
break;
}
}
