RE: [IBIS] Question regarding V-t tables

Bob,

Regarding #2, I think you misunderstood it a little. The point
was not to find a mechanism to model pre/de-emphasis buffers.
I am aware of those options you mentioned, and the purpose of
this discussion was not to replace those options. The goal
of this idea was to improve on the accuracy of such models
which use those options without having to use *-AMS.

However, from a private message I was reminded to the IV and Vt
curve matching issue which throws a monkey wrench into this
idea. The problem is that if I made multiple Vt curves using
the same Rfixture Vfixture combination and the swing of the
Vt curves are not the same, they would require a different
IV curve to satisfy Ohm's law. In other words this selection
mechanism could not be applied to Vt curves alone, it would
also have to be extended to IV curves. This would introduce
a much bigger change to the spec than I think is worth it.

So it sounds like this was a nice try but it may not be feasible.

Regarding #1, I get your point. If this is not a concern, we
can leave it the way it is.

Thanks,

Arpad
===============================================================

-----Original Message-----
From: Bob Ross [mailto:bob@teraspeed.com]
Sent: Thursday, September 09, 2004 12:25 PM
To: Muranyi, Arpad
Cc: ibis@eda.org
Subject: Re: [IBIS] Question regarding V-t tables

Arpad:

There are several implications and threads with respect to
the original question and proposed solutions. Data dependent
results in (2) seem to indicate pre-emphasis/de-emphasis
which can be modeled by current switching or [Driver Schedule]
approximations or *-AMS formulations instead of waveform
selections. So I question whether (2) is even a good approach
vs alternatives.

Regarding (1) the specification has holes in it based on
non-practical situations. Yes, we could document a few more
restrictions, if they are really issues in industry. However,
our efforts might be better spent on other things.

For fun, the file at the end is legal and passes ibischk4
with zero errors and warnings as a Version 2.1, 3.2 and 4.0
IBIS file. So what is wrong with it? I wonder what EDA
tools do with it.

Bob

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Received on Thu Sep 9 12:56:31 2004