RE: [IBIS-Users] way to extract rising and falling waveform in differential cells

Hello, Akilesh,

One might build a separate model for each frequency. However, as Andy
points out, a model built at one frequency will NOT correlate well between
SI simulators and SPICE. Overclcoked models are handled differently by
different SI simulators, so the quality of comparison would depend on the
simulator.

The parser makes few checks on table data. So models can pass the parser
even when the data is "bad" or incomplete. You might want to use the IBIS
Quality Checklist, which contains additional checks (some of them
manual).http://www.sisoft.com/ibis-quality/

Best regards,

Lynne

"IBIS training when you need it, where you need it."

Dr. Lynne Green

Green Streak Programs

http://www.greenstreakprograms.com

425-788-0412

lgreen22@mindspring.com

  _____

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of Akhilesh CHANDRA
Sent: Sunday, December 19, 2004 7:40 AM
To: Andrew Ingraham
Cc: ibis-users@eda.org; Akhilesh CHANDRA
Subject: Re: [IBIS-Users] way to extract rising and falling waveform in
differential cells

Hello Andy,

 That means we can't make IBIS model that work at 1ghz. I think we can make
IBIS models at such high frequency. Now I put both rising and falling
database in my model and it is parsed by golden parser without any problem
but still result are not good at 622Mhz.
  Is this also problem from simulator. I am using eldo (AMS CADENCE)for
validation.

Regards
Akhilesh

Andrew Ingraham wrote:

Akhilesh,

In the example you gave earlier, the simulation was at 250 MHz (2 ns high
and 2 ns low) and the waveform had just about reached the other state when
it was being switched again. Attempting to simulate this much faster (622
MHz or 1 GHz), with IBIS, is probably doomed to failure because of IBIS's
limitations. This is sometimes known as "over-clocking" the IBIS model,
because the model hasn't reached the other state yet when it is being
clocked again in the other direction. Some simulators handle this situation
very poorly, so you could see very poor IBIS vs. SPICE correlation at such
faster frequencies.

Regards,

Andy

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Received on Sun Dec 19 12:11:58 2004