Subject: BIRD 6.1

From: Kellee Crisafulli <[email-masked]>
Date: 30 Jan 94 19:49:07 EST

From: Kellee Crisafulli, HyperLynx Inc.

Re: Bird 6.1

This is a big improvement over 6.0, good work.

As I read through 6.1, I notice something that concerned how various
simulators would determine how to launch the waveform to make sure
the skew time is correct as measured at the center point of the
voltages.  I believe this will be very difficult to accomplish.  The
load values and differences in how various simulators launch the
edge transitions will probably cause the skew to be all over the
place.  The present output buffer specification does not specify
where the edge actually starts relative to t=0 seconds.  I know for
a fact that there is a difference between at least 3 of the simulators
that presently run IBIS files.

Could we reference this skew time to where the simulators launch
the edge changes.  This should roughly correlate to the center
points, however it may be slightly different depending on load
conditions and simulators.  This however would be reasonable for
all simulators.  The semiconductor companies could still measure
at the center point with a fixed load.  This will have some accuracy
errors, however I believe that keeping it simple will allow everyone
concerned to get it working quickly and easily and that is worth alot!

If we use this method, I believe we should specify how to measure it,
and how to simulate it.