// global system clock
public void Clock()
{
ppu.Clock();
if (clockCounter % 3 == 0)
{
if (dmaStarted)
{
if (dmaDummy)
{
if (clockCounter % 2 == 1)
{
dmaDummy = false;
}
}
else
{
if (clockCounter % 2 == 0)
{
UInt16 address = BitMagic.Combine(dmaPage, dmaAddress);
dmaData = CpuRead(address);
}
else
{
ppu.Oam[dmaAddress++] = dmaData;
// after 256 writes dmaAddress loops back to zero
if (dmaAddress == 0)
{
dmaStarted = false;
dmaDummy = true;
}
}
}
}
else
{
cpu.Clock();
}
}
if (ppu.EmitNmi)
{
cpu.NMI();
}
clockCounter++;
}