[IBIS] Question regarding V-t tables

All,

I just realized something regarding the V-t tables in IBIS that raises
a question in my mind.

The spec says that we can have up to 100 V-t tables. It doesn't say
anything on how Vfixture and Rfixture should be selected for these to
make a good model.

Many simulators can only support the first four tables, but I am aware
of some which can make use of all of them. As far as I know, the
algorithms which make use of all of them assume that the additional
tables generated with the various Rfixture and Vfixture values provide
a better understanding for how the buffer reacts to various loading
conditions.

What I would like to find out is this: What would happen if an IBIS
file had multiple V-t tables with repeated Rfixture and Vfixture
parameters, but different waveform shapes? (This ***CAN*** happen
nowadays with advanced buffers which exhibit data pattern dependent
behaviors). Obviously, given the current spec, the tool wouldn't
know when to use which table. Would this be a good reason to write
another BIRD for some additional subparameters for the V-t tables?

Arpad
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Received on Wed Sep 8 11:44:48 2004