RE: [SI-LIST] : IBIS Subcommittee Formed to Review Spice to IBIS

Beal, Weston ([email protected])
Mon, 7 Jun 1999 09:12:10 -0500


I think this is a worthy endeavor and I applaud your goal. I've been using
s2ibis2q (my Compaq version of s2ibis2) for a couple of years, and have a
few particular items that I see as weaknesses. The three items which I
fixed were easy and didn't take much time. First the default of 2
significant digits in the spice output was much too little. I changed it to
5 digits and have seen good results. In reality, this should probably be
configurable from the control file.
The second thing that I fixed was to subtract both the power clamp and
ground clamp curves from the pullup and pulldown curves. In general, this
is not needed, but I don't want it to bite me in the shorts when I'm not

The third thing that I changed was the number of points in the time
waveforms from 50 to 101. I have to remove one point to comply with the
golden parser, but I get better detail. On the issue of number of points in
a curve or waveform, I think the user should be able to define any degree of
granularity and the IBIS creator tool should have an algorithm to remove
points in linear regions. If the resulting curve still has too many points,
then increase the linearity tolerance and try it again.

One other thing that bothers me is that the data input files (spice output
files) must have the same number of data points at the same voltage or time
values. I realize that it would take a bit more work, but I would expect to
be able to give any three sets of data and have the IBIS creator interpolate
and extrapolate as needed in order to create complete IBIS tables. This is
not needed when your spice models behave nicely, but how often does that
happen? Most of the time, my spice simulations do not converge very far
outside the normal operating range and I am forced to fake data or cut off
the good data to the same range as the problem data.

Weston Beal
Signal Integrity Engineer
Compaq Computer Corp.

-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: Friday, 04 June, 1999 4:26 PM
To: [email protected]; [email protected]
Subject: [SI-LIST] : IBIS Subcommittee Formed to
Review Spice to IBIS

Hello everyone.

On May 28, 199, the IBIS Committee, via the IBIS Open Forum
formed a subcommittee to determine the viability of taking
ownership of the
Spice to IBIS (s2ibis2) tool, originally written at North
Carolina State
University. This subcommittee will eventually report back
to the IBIS Committee
the following:
1. Any known bugs with the current tool.
2. Any future enhancements for the next generation tool

From these lists, the IBIS Committee and this subcommittee
will draft a
"requirements" list, and pending funding, request bids from
various sources to
update/rewrite the tool. Like the IBIS Parser, we want to
keep the Spice to
IBIS tool in the public domain (open source).

As chairperson of this subcommittee, I am asking for your
help. If you are a
user, or one of the many programmers, of the current Spice
to IBIS tool, I am
looking for your feedback to make the next tool better. If
you know of any
bugs, or have any enhancement requests, please let us know
by posting your
comments to either the IBIS or SI reflector. If you wish to
keep your comments
psuedo-confidential, please feel free to send them directly
to myself at
"[email protected]". Please be as specific as you can. In
the case of bug
reports, we may need to contact you off-line to get more
information and/or

Please send your responses no later than June 18, as we will
be discussing this
topic at the IBIS Summit Meeting, which will be held Monday,
June 21.

Disclaimer: all participants on this subcommittee, as well
as those on the IBIS
Committee, are volunteers, attempting to make this tool
better. We are not
getting paid, nor receiving any benefits, from this work.
So please, be kind
with your comments.

Michael Cohen

IBM Personal Systems Group
Design Tools Department
3039 Cornwallis Road
Research Triangle Park, NC 27709

Phone: 919-543-4042 (T/L 441-4042)
FAX: 919-543-8221 (T/L 441-8221)
Internet Address: [email protected]

IBM Internal Addresses:
From Lotus Notes (#1): Michael Cohen/Raleigh/IBM
From Lotus Notes (#2): [email protected]
From VM: [email protected]

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