public byte Read(int port)
{
if (port == PORT_CONTROL)
{
throw new InvalidOperationException();
}
if (port == PORT_COUNT0)
{
return(CountZero.Read());
}
else if (port == PORT_COUNT1)
{
return(CountOne.Read());
}
else if (port == PORT_COUNT2)
{
return(CountTwo.Read());
}
else if (port == PORT_STATUS)
{
if (_timerHack.Count > 0)
{
return(_timerHack.Dequeue());
}
return((byte)((timerZero ? 1 : 0) + ((timerOne ? 1 : 0) << 1)));
}
throw new InvalidOperationException();
}
public void Step(double us)
{
_us += us;
if (_us >= CLK_US)
{
var beforeZero = CountZero.Output;
CountZero.Pulse();
if (!beforeZero && CountZero.Output && CountZero.Active)
{
CountOne.Pulse();
}
CountTwo.Pulse();
if (CountZero.Output && CountZero.Active)
{
timerZero = true;
}
if (CountTwo.Output && CountTwo.Active)
{
timerOne = true;
}
_us -= CLK_US;
}
}
public void Write(int port, byte data)
{
if (port == PORT_CONTROL)
{
Counter counter = null;
var counterNum = (data >> CTL_SEL_SHIFT) & CTL_SEL_MASK;
var readLoad = (data >> CTL_RL_SHIFT) & CTL_RL_MASK;
var mode = (data >> CTL_MODE_SHIFT) & CTL_MODE_MASK;
var bcd = (data & 1) == 1;
if (counterNum == 0)
{
counter = CountZero;
}
else if (counterNum == 1)
{
counter = CountOne;
}
else if (counterNum == 2)
{
counter = CountTwo;
}
counter.ReadLoad = (CounterReadLoad)readLoad;
counter.Mode = (CounterMode)mode;
counter.BCD = bcd;
if (counter.Mode == CounterMode.Mode0 && counter.ReadLoad != CounterReadLoad.Latch)
{
counter.Value = counter.LastWrittenValue;
}
if (counterNum != 1)
{
counter.Active = false;
}
if (bcd)
{
throw new NotImplementedException();
}
if (counter.ReadLoad == CounterReadLoad.Latch)
{
counter.LatchedValue = counter.Value;
}
}
else if (port == PORT_COUNT0)
{
timerZero = false;
CountZero.Write(data);
}
else if (port == PORT_COUNT1)
{
//this is a hack
CountOne.Value = 250;
CountOne.LastWrittenValue = 250;
CountOne.Active = true;
//CountOne.Write(data);
}
else if (port == PORT_COUNT2)
{
timerOne = false;
CountTwo.Write(data);
}
else if (port == PORT_STATUS)
{
timerZero = timerZero && (data & 1) == 1;
timerOne = timerOne && (data & 2) == 2;
}
}
