RE: [SI-LIST] : Verifying IBIS models

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From: Brad Crowell (crowell@amirix.com)
Date: Tue Dec 05 2000 - 05:09:12 PST


Christoph,

An IBIS file for an output buffer can include data tables for a rising and
falling waveform. These are included to allow the user to correlate the
simulation output to these "golden waveform" which were originally developed
from the Spice deck for the buffer or actual measurements. That's the short
answer, for a longer version check out the IBIS Accuaracy Handbook available
on the IBIS website:

http://www.eigroup.org/ibis/ibis.htm

Brad

> -----Original Message-----
> From: owner-si-list@silab.eng.sun.com
> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Christoph Hillen
> Sent: Tuesday, December 05, 2000 3:25 AM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Verifying IBIS models
>
>
>
>
> mm...
> can anyone explain the "golden waveform" ??
>
> Christoph Hillen
>
>
>
>
>
> "Gregory R Edlund" <gedlund@us.ibm.com> on 04.12.2000 22:34:04
>
> Please respond to "Gregory R Edlund" <gedlund@us.ibm.com>
>
> To: si-list@silab.eng.sun.com
> cc: (bcc: Christoph Hillen/Aachen/Utimaco/DE)
>
> Subject: [SI-LIST] : Verifying IBIS models
>
>
>
> Hello Brad,
>
> I am one of the folks who worked on the I/O Buffer Accuracy Handbook
> (formerly IBIS Accuracy Specification). Let me try to address your
> questions.
>
> 1. I don't know how widely used our work is, but I have talked to a
> handful of people who are using it. It's hard to say what most people are
> doing with it; the sample size isn't very large!
>
> 2. I have written a C program that reads two waveform files and computes
> the figure of merit we documented in the Handbook. It also does two other
> computations since the first one can be misleading in certain cases. I
> just secured permission from my company to publish this code as freeware.
> If you can wait a few days, I'm planning to have it on the IBIS web site
> next week (if our web master is available). Of course, visual checks are
> always helpful, too. We still haven't built a computer that
> comes close to
> the human brain!
>
> 3. So far I have not seen this procedure used in any simulation tools,
> although I've talked to three different EDA people who have shown an
> interest in pursuing it. Perhaps you should call your local rep! :) One
> hang-up we found in trying to store a "golden waveform" in an IBIS file is
> that the simulator actually tries to use the data in constructing its
> stimulus waveform. Ugly simulations result. What we really need is some
> syntactical construct in IBIS that says, "This is a golden
> waveform." I've
> been thinking about authoring a BIRD (IBIS buffer issue resolution
> document) to get this syntax into IBIS. (Too many irons in the fire.) We
> would also need a modification to s2ibis2 that creates these golden
> waveforms using the new IBIS syntax. These things would go a long way
> toward improving the accuracy of model data, eh?
>
> Greg Edlund
> Advisory Engineer
> Electrical Packaging
> IBM Server Technology Development
> 3605 Hwy. 52 N, Dept. HDC
> Rochester, MN 55901
> gedlund@us.ibm.com
>
>
> Date: Fri, 1 Dec 2000 11:45:40 -0400
> From: "Brad Crowell" <crowell@amirix.com>
> Subject: [SI-LIST] : Verifying IBIS models
>
> I am wondering how the verification of an IBIS model is being handled. The
> accuracy spec provides the "golden waveforms" that a simulation output can
> be checked against, but how is this checking being done by most people? Is
> this just a visual check or are there some tools out there that
> can provide
> a quantitative measure of the model's accuracy? Is this feature
> included in
> some of the simulation tools?
>
> Thanks for your comments,
> Brad
> ***************************************
> Brad Crowell
> Hardware Designer
> AMIRIX Systems
> 77 Chain Lake Drive
> Halifax, Nova Scotia, B3S 1E1
> Tel: (902) 450-1700 ext#287
> Fax: (902) 450-1704
> Email: crowell@amirix.com
> Web: http://www.amirix.com
>
>
>
>
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