// Expected to be called at the rate of the base clock of 4,194,304 Hz.
public void Tick()
{
// DIV counter
_divCounter++;
if (_divCounter == 256)
{
_divCounter = 0;
_div++;
}
// TIMA counter
if (!_timerEnabled)
{
return;
}
_timerCounter++;
if (_timerCounter == _timerDivider)
{
_timerCounter = 0;
_timer++;
// overflow happened
if (_timer == 0)
{
_timerInterrupt.Trigger();
_timer = TMA.Value;
}
}
}
private void ChangeMode(LcdMode newMode)
{
_currentMode = newMode;
_counter = 0;
if (newMode == LcdMode.OamSearch)
{
if (_stat.OamSearchInterruptEnabled.Value)
{
_lcdStatusInterrupt.Trigger();
}
}
else if (newMode == LcdMode.DataTransfer)
{
// Do nothing.
}
else if (newMode == LcdMode.HorizontalBlank)
{
RenderScanline(_ly.Value);
if (_stat.HBlankInterruptEnabled.Value)
{
_lcdStatusInterrupt.Trigger();
}
}
else if (newMode == LcdMode.VerticalBlank)
{
//Console.WriteLine($"Vblank after {_globalCounter - _lastVblank} cycles.");
_lastVblank = _globalCounter;
OnCompletedFrame();
_vblankInterrupt.Trigger();
// TODO does vblank really have two interrupts?
if (_stat.VBlankInterruptEnabled.Value)
{
_vblankInterrupt.Trigger();
}
}
}
// TODO: Make this more efficient. Currently one clock per call.
// TODO: Timing is not accurate. (Depends on sprite count etc)
public int Tick()
{
if (!_lcdc.LcdEnabled.Value)
{
return(1);
}
_counter++;
_globalCounter++;
switch (_currentMode)
{
case LcdMode.OamSearch:
if (_counter >= 80)
{
ChangeMode(LcdMode.DataTransfer);
}
break;
case LcdMode.DataTransfer:
if (_counter >= 172)
{
ChangeMode(LcdMode.HorizontalBlank);
}
break;
case LcdMode.HorizontalBlank:
if (_counter >= 204)
{
_ly.Value++;
if (_ly.Value == 144) // TODO maybe 143???
{
ChangeMode(LcdMode.VerticalBlank);
}
else
{
ChangeMode(LcdMode.OamSearch);
}
}
break;
case LcdMode.VerticalBlank:
// TODO this is wrong, maybe?
if (_counter >= 456)
{
_ly.Value++;
_counter = 0; // TODO re-check
}
if (_ly.Value == 154)
{
_ly.Value = 0;
ChangeMode(LcdMode.OamSearch);
}
break;
}
if (_ly.Value == _lyc.Value && _stat.ScanlineCoincidenceInterruptEnabled.Value)
{
_lcdStatusInterrupt.Trigger();
}
_stat.Mode = _currentMode; // TODO
return(1);
}
