private static string DisassembleEmulatorBusSource(MicroInstruction instruction, out bool loadS)
{
EmulatorBusSource bs = (EmulatorBusSource)instruction.BS;
switch (bs)
{
case EmulatorBusSource.ReadSLocation:
loadS = false;
if (instruction.RSELECT == 0)
{
return("M");
}
else
{
return(String.Format("$S{0}", Conversion.ToOctal((int)instruction.RSELECT)));
}
case EmulatorBusSource.LoadSLocation:
loadS = true;
return(String.Empty);
default:
loadS = false;
throw new InvalidOperationException(String.Format("Unhandled Emulator BS {0}", bs));
}
}
protected override ushort GetBusSource(MicroInstruction instruction)
{
EmulatorBusSource ebs = (EmulatorBusSource)instruction.BS;
switch (ebs)
{
case EmulatorBusSource.ReadSLocation:
if (instruction.RSELECT != 0)
{
return(_cpu._s[_rb][instruction.RSELECT]);
}
else
{
// "...when reading data from the S registers onto the processor bus,
// the RSELECT value 0 causes the current value of the M register to
// appear on the bus..."
return(_cpu._m);
}
case EmulatorBusSource.LoadSLocation:
// "When an S register is being loaded from M, the processor bus receives an
// undefined value rather than being set to zero."
_loadS = true;
return(0xffff); // Technically this is an "undefined value," we're defining it as -1.
default:
throw new InvalidOperationException(String.Format("Unhandled bus source {0}", instruction.BS));
}
}
protected override ushort GetBusSource(MicroInstruction instruction)
{
//
// The Trident tasks are wired to be RAM-enabled tasks so they can use
// S registers.
// This code is stolen from the Emulator task; we should REALLY refactor this
// since both this and the Orbit Task need it.
//
EmulatorBusSource ebs = (EmulatorBusSource)instruction.BS;
switch (ebs)
{
case EmulatorBusSource.ReadSLocation:
if (instruction.RSELECT != 0)
{
return(_cpu._s[_rb][instruction.RSELECT]);
}
else
{
// "...when reading data from the S registers onto the processor bus,
// the RSELECT value 0 causes the current value of the M register to
// appear on the bus..."
return(_cpu._m);
}
case EmulatorBusSource.LoadSLocation:
// "When an S register is being loaded from M, the processor bus receives an
// undefined value rather than being set to zero."
_loadS = true;
return(0xffff); // Technically this is an "undefined value," we're defining it as -1.
default:
throw new InvalidOperationException(String.Format("Unhandled bus source {0}", instruction.BS));
}
}
