FW: FW: Spice Model of IBIS

Thank you to all those members who provided me with feedback regarding the
use of SPICE for behavioral simulation. What I found interesting was
everyone agreed that SPICE can be used to do exactly what IBIS was intended
to do, however no standard SPICE syntax exists to make the model available
across different platforms.

I have included a response I obtained from my SPICE vendor as I believe it
provided further insight to the issues, and presents several possible
solutions. I'm not sure I agree with his conclusion, because if members of
this newsgroup and other SPICE users are willing to choose one of the
solutions presented below, most SPICE vendors lacking this functionality
would probably add this to their product.

Since multiple vendors support XSPICE syntax, then why not use a syntax
based on XSPICE to implement a behavioral model?

Regards

John Synesiou jsynesio@us-power.com
U.S. Power, Inc Phone (612)826-1111
6497 City West Parkway Fax (612)826-1003
Eden Prairie Date: 03/30/98
MN, 55344 Time: 7:23 PM

John
I could write a novel in response to some of these emails. But a couple of
points.
As a spice vendor we are committed to supporting IBIS. It's really not that
big a deal for SPICE vendors to make subcircuits from IBIS data sheets.
While we have made IBIS to spice conversions for customers, the task was
rather timeconsuming and manual. We will be putting out a software utility
to do the job. Syntactically IBIS is a good standard that spice vendors can
use to make models. The other issue of IBIS tools being better solution for
pcb analysis is a NON-ISSUE as far as IBIS syntax is concerned. A spice
engine could be fitted with all such features so IBIS tools really have no
inherent advantage. The underlying syntax would in any case be transparent
to the user. Users should be able to use their SPICE simulators if they want
to. If features to do a job are lacking in SPICE products that's a
completely different question.
As for SPICE, it is far more than a functional simulator. People who think
otherwise need to wake up. They are living in the past by 5-10 years. Today
spice simulators handle C code, ActiveX servers, Visual basic scripts, as
well as full behavioral circuit descriptions using math equations,
if-then-else statements, and table models. Virtually every commercial SPICE
program has a full behavioral simulation capability allowing system, board
and IC design to be simulated in ANY combination.
With regard to a SPICE standard. True there is no standard spice behavioral
syntax. I was able to derive a SPICE model from an IBIS data sheet using
SPICE 2G6 syntax (See May 1993 Intusoft Newsletter). This would be
compatible with ALL SPICE simulators. So this is one possibility. The
Berkeley SPICE B element is the closest thing to a standard in the SPICE 3
world. The syntax problem is largely due to other SPICE vendors lack of
desire to be cooperative (this is not sour grapes, its the hard truth. All
attempts to get them to change\adapt to Berkeley spice or XSPICE syntax have
met with indifference). But XSPICE, from Georgia Tech, could be the
standard EVERYONE is looking for. Its public domain, its used by seven
different SPICE vendors (Intusoft, Deutsch, Cad-Migos, Visionics, Electronic
Workbench, Circuit maker), it hides the model implementation because its
compiled (good for vendors), and the language is based on the most popular
AHDL there is; C. The C part could make the model easily portable to those
tools, SPICE or other, that don't have XSPICE.
With regard to the need for IBIS, I stated from the outset when IBIS was
being developed that a SPICE description could be found to solve the
problem. Indeed, in most cases, the SPICE description DOES NOT reveal any
hidden secrets about the technology or device architecture. These types of
claims are usually made by people who only know SPICE as a transitor level
simulator. They are often ignorant of SPICE's ability to model behavior in
various ways as to hide the real circuits nature. Clearly, it is possible to
even use a transistor topology since Philips, Texas Instruments, and
Motorola freely distribute model done in this fashion. However, silly,
people refuse to extend SPICE, probably because its syntax is not IEEE
controlled. I wish it were. Anyway IBIS is here to stay.
Received on Mon Mar 30 18:46:54 1998