public DMAController(IOProcessor iop)
{
_iop = iop;
for (int i = 0; i < _channels.Length; i++)
{
_channels[i] = new DMAChannel();
}
}
/// <summary>
/// Executes a single DMA transfer (if there are
/// any transfers pending). This takes 4 clock
/// cycles.
/// </summary>
public void Execute()
{
//
// See if there's anything to do.
//
int nextChannel = SelectNextChannel();
//
// Raise HRQ if so.
//
_hrq = nextChannel != -1;
if (_hrq)
{
DMAChannel c = _channels[nextChannel];
if (Log.Enabled)
{
Log.Write(LogComponent.IOPDMA, "Channel {0} selected. {1} bytes to {2}, addr 0x{3:x4}.",
nextChannel, c.ChCount, c.Type, c.ChAddr);
}
switch (c.Type)
{
case DMAType.Verify:
throw new NotImplementedException("DMA Verify not implemented.");
case DMAType.Read:
// Read byte from memory and transfer to device
byte dmaWrite = _iop.Memory.ReadByte(c.ChAddr);
c.Device.DMAWrite(dmaWrite);
if (Log.Enabled)
{
Log.Write(LogComponent.IOPDMA, "DMA read transfer of byte 0x{0:x2} from address 0x{1:x4}", dmaWrite, c.ChAddr);
}
break;
case DMAType.Write:
// Read byte from device and transfer to memory.
byte dmaRead = c.Device.DMARead();
_iop.Memory.WriteByte(c.ChAddr, dmaRead);
if (Log.Enabled)
{
Log.Write(LogComponent.IOPDMA, "DMA write transfer of byte 0x{0:x2} to address 0x{1:x4}", dmaRead, c.ChAddr);
}
break;
}
// Increment address, decrement counter.
c.ChAddr++;
c.ChCount--;
// If the counter runs out, stop the channel if so enabled.
if (c.ChCount == 0)
{
if (Log.Enabled)
{
Log.Write(LogComponent.IOPDMA, "Channel {0} completed.", nextChannel);
}
// Stop this crazy thing.
if (_tcStop)
{
c.Enabled = false;
if (Log.Enabled)
{
Log.Write(LogComponent.IOPDMA, "Channel {0} disabled.", nextChannel);
}
}
c.Completed = true;
c.Device.DMAComplete();
}
_lastSelectedChannel = nextChannel;
}
}