[SI-LIST] Re: PCI-X 1.0a simulation

  • From: "Andrew Ingraham" <a.ingraham@xxxxxxxx>
  • To: <si-list@xxxxxxxxxxxxx>
  • Date: Tue, 27 Dec 2005 10:33:10 -0500


> In my circuit there are two devices PCI-X 1.0a driver and receiver.
> I have IBIS model for receiver.
> I don't have IBIS model for driver.

Don't forget, most PCI-X signals are bi-directional.  If you have one
device's models, it should be both a receiver and a driver.

PCI-X buffers, like PCI buffers, are bounded by a specification, and one
*should* not have a buffer whose I/V curves exceed those bounds.

In theory, therefore, one could construct a generic PCI-X IBIS model or
models that display the best- and worst-case characteristics in some manner.
Then, in principle, one could use that model in simulations, in lieu of a
real device model, and hope that your real PCI-X device is somewhere between
the extremes displayed by the generic model.

While this can be done, and it is better than doing nothing until you have a
real model, I'd use the results with a lot of caution.  Simulate, then apply
liberal margins.  Some devices do exceed the limits in the specs.  Press
your ASIC vendor for a real model.

And I'd be especially cautious about using the models for some other PCI-X
device as a "stand-in" for your device's model.  (Still, however, it is
better than nothing.)

Is this a hard-wired or embedded bus with fixed devices on both ends?  The
more usual case is a bus with connector(s), allowing any device to be
plugged in on the other end.  In that case, one can't simulate the bus with
every possible PCI or PCI-X card out there, so generic models are the only
practical way to do it, along with a handful of simulations using some
actual device models you have available.

If your bus has a connector, don't forget that a PCI device can be plugged
into it too, and PCI's range of drive strengths (V/I curves) is wider than


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