Subject: low budget IBIS tools

From: ram <[email-masked]>
Date: Thu, 12 Jun 1997 19:19:31 -0700

are there such a thing?  I'm doing a 40 Mhz microprocessor design which
looks like it has some potential problems with the bus layout.  I'd
rather not spend the 5 to 50K for modelling tools if I can help it.  Are
there any lower cost IBIS to spice convertors out there? And is the
conversion accurate (i.e., do you lose information in the conversion
from IBIS to spice), or should I be looking for native-mode tools?

Thanks in advance.

Rick McBain
Senior Engineer
Dynamic Control Syetms Inc.

---

From: Kellee Crisafulli <[email-masked]>
Date: Sat, 18 Oct 1997 10:16:07 -0700

Hi Rick,

>from IBIS to spice), or should I be looking for native-mode tools?

Our Visual IBIS editor is free.

Our Simulators do not require a conversion to spice and
start at less than 3K, See www.hyperlynx.com

---

From: Kellee Crisafulli <[email-masked]>
Date: Thu, 23 Oct 1997 22:59:51 -0700

This email group is for IBIS uses only!  please
take product specific email off or do it privately.

At 09:59 AM 10/24/97 +0800, weberchuang wrote:
>
>   Can I know to what level of MOS models that the AMP-spice can
>support? Thanks!
>
>Weber Chuang
>SI eng. 
>VIA tech. Taiwan, ROC
>
>

---

From: [email-masked] (Dan Aleksandrowicz)
Date: Fri, 24 Oct 1997 08:30:02 -0400 (EDT)

Hi there.

Kellee is right, we all, once in a while, want to show and tell
about our specific products or services. However, we have a 
fragile common goal and a lot of sensitivity is required.

There are no specific "rules" or guidelines about what is
right or wrong for this mail group, which I think is vital
to the free discussion. 

However, I feel that in general problems and solutions that 
are not EDA tool specific, were and are the essence of this mail group. 

And from my experience, any EDA tool specific problems and 
solution are most efficiently handle out side this group. 

Thanks

Dan Aleksandrowicz
KAW/USA

---

From: "fabrizio zanella" <fabrizio=[email-masked]>
Date: Fri, 24 Oct 97 9:51:21 -0400

Tom, the problem is that some semiconductor vendors are starting to only 
make IBIS models available, they don't want to release SPICE models (at 
times they release them under NDA, which is a nuisance for it can take up 
to a month to get all the signatures).
  I use HSPICE for computer system signal integrity analysis and have found 
very good correlation to empirical measurements. I have many device HSPICE 
models which are quite accurate.  The few IBIS tools available are 
completely different and incompatible with SPICE files.   I therefore want 
to continue using HSPICE, but run into a problem at times if I can only get 
IBIS models.
Does anyone have any thoughts on this?  
Thanks, 
Fabrizio Zanella
									Sr. Design Engineer
									Hardware Engineering
			                          _/ _/  email: 
[email-masked]
       _/_/_/_/  _/     _/   _/_/_/     _/    voice: (508) 435-1000 Ext. 
4645
      _/        _/_/ _/_/  _/        _/          Fax: (508) 435-8949
     _/_/_/_/  _/  _/ _/  _/      _/_/_/
    _/        _/     _/  _/                       EMC Corporation
   _/_/_/_/  _/     _/    _/_/_/                  171 South Street
                                                Hopkinton, MA 01748-9103
-------------
Original Text
From: "Tom Warneke" <[email-masked]>, on 10/24/97 8:29 AM:
To: smtp@Eng@EMCHOP1["[email-masked]'" <[email-masked]>]

Hi,
I am perplexed why one would want to convert IBIS to Spice models.

My experience has been that digital designers (which IBIS is intended to
serve) want to move away from SPICE to tools better suited to analyzing
signal integrity, cross-talk, and EMC -- the annoying by-products of
high speed digital circuits and fast edge rate devices that are common
today.

SPICE is a valuable tool for the analog engineer, and gives accurate
results to the experienced user that understands the modeling
requirements; however, it has not been the most effective tool for doing
large scale signal integrity analysis on PCBs which is becoming more and
more necessary on today's digital designs.

In addition, IBIS models are often converted from SPICE.  Why not
request the SPICE models directly?

All comments welcome,
Tom
-- 
Tom Warneke
CAD Application Engineer
Cisco Systems
250 Apollo Drive
Chelmsford, MA 01824
email: [email-masked]
Phone: 508-244-8214
  FAX: 508-244-8347

fabrizio zanella wrote:
> 
> Ted,  regarding the IBIS to SPICE conversion in the AMPredictor tool;
> is the SPICE behavioral model output a file which can also be read by 
tools
> like HSPICE, PSPICE?  How do you verify the accuracy of the IBIS models 
and
> also have you verified if any critical information has been lost in the
> conversion process?
> Does anyone else out there know of any other tools which are available 
for
> sale which convert IBIS files to HSPICE or PSPICE formats?
> Thanks,
>                                                                         
Fabrizio Zanella
Sr. Design Engineer
Hardware Engineering
>                                                   _/ _/  email:
> [email-masked]
>        _/_/_/_/  _/     _/   _/_/_/     _/    voice: (508) 435-1000 Ext.
> 4645
>       _/        _/_/ _/_/  _/        _/          Fax: (508) 435-8949
>      _/_/_/_/  _/  _/ _/  _/      _/_/_/
>     _/        _/     _/  _/                       EMC Corporation
>    _/_/_/_/  _/     _/    _/_/_/                  171 South Street
>                                                 Hopkinton, MA 01748-9103
> -------------
> Original Text
> From: "Lin, Ted" <[email-masked]>, on 10/23/97 5:56 PM:
> To: smtp@Eng@EMCHOP1["[email-masked]'" <[email-masked]>],
> smtp@Eng@EMCHOP1["'ram'" <[email-masked]>]
> 
> Hi Rick,
> 
> AMP Inc. offers a signal integrity tool called the AMPredictor Signal
> Integrity Analyzer. ($8,500 for a single license, $5,000 a piece if
> you purchase 3 licenses.)  It is a Spice-based pre-layout tool that
> includes a complete Spice engine, a 2-D field solver that generates
> coupled-lossy transmission line models, connector noise analyzer, and
> an IBIS-to-AMPSPICE converter.  The software can convert an IBIS data
> file to a SPICE-format analog behavior model.  It then can be used
> with the AMPSPICE engine to perform Spice-based critical net analysis.
> 
> There is more information on the website.
> www.ampincorporated.com/ampredictor
> 
> ----------
> From:  ram [SMTP:[email-masked]]
> Sent:  Thursday, June 12, 1997 10:20 PM
> To:  [email-masked]
> Subject:  low budget IBIS tools
>

---

From: Andrew Ingraham <[email-masked]>
Date: Fri, 24 Oct 97 11:37:51 EDT

> Does anyone have any thoughts on this?  

I agree 100% !!!

Today I need a SPICE model for an 8-pin part.  We either take their IBIS
model or we wait a month for the NDA.  But I need the SPICE model!

---

From: [email-masked]
Date: Fri, 24 Oct 1997 14:08:50 -0500

Greetings,

     Might I suggest a couple reason's
     
     1.  Some people only have one "solver"  SPICE or IBIS..'  
     
     2.  Some models might only come in one of the two versions... 
     therefore a translator is required.  For example, digital IC companies 
     like to provide IBIS models because they do not reveal manufacturing 
     processes.
     
     3. Someone might be interested in MULTIPLE coupled line effects  
     (electrostatic AND magnetic) for analog or digital designs.  The IBIS 
     standard format does not have a format to do this ... yet??..  SPICE 
     does...
     
     Are there other reasons?
     
     _gus  panella
     Molex, Inc.

______________________________ Reply Separator _________________________________
Subject: Re: low budget IBIS tools
Author:  [email-masked] at internet 
Date:    97/10/24 8:29 AM

Hi,

     

All comments welcome,
Tom

fabrizio zanella wrote:
> is the SPICE behavioral model output a file which can also be read by tools 
> like HSPICE, PSPICE?  How do you verify the accuracy of the IBIS models and 
> Does anyone else out there know of any other tools which are available for 
>                                                                         Fabriz
io Zanella
>                                                                         Sr. De
sign Engineer
>                                                                         Hardwa
re Engineering

---

From: Andrew Ingraham <[email-masked]>
Date: Sat, 25 Oct 97 22:40:51 EDT

> high speed digital circuits and fast edge rate devices that are common

I disagree that IBIS is intended to serve digital designers who want
to move away from SPICE.  IBIS has everything to do with analog
simulation, the same stuff we use SPICE for.  IBIS models are not
inherently different from SPICE models in terms of signal integrity,
crosstalk, EMC, etc.

One of the reasons for IBIS is because of the proprietary model
problem.  Lots of us folks who use SPICE, have this problem, both
analog and digital engineers.  Quoting from the IBIS FAQ: "IBIS ... is
a method of providing the Input/Output device characteristics through
V/I data without disclosing any circuit/process information."

Another reason is speed.  SPICE models can be unnecessarily complex,
when all you are after are the interconnect characteristics.  Some
SPICE models include the whole chip, or huge portions of the output
buffers, and run unbearably slow.  IBIS focuses only on the I/O
characteristics.

Yet another reason, is that IBIS models lend themselves particularly
well to being based on real, measured data.  Trying to tweak a
full-blown SPICE model to fit measured data, is risky at best.  IBIS
models don't need to be tweaked to fit the data; the measured data
becomes the IBIS model.

In my opinion, the free s2ibis tool, has done a lot to damage IBIS's
potential, by allowing anyone to make IBIS models from their SPICE
models and not even trying to use measured data.  s2ibis is how you
jump on the IBIS bandwagon.  It's not how you do it right.

On the other hand, a free i2spice tool, is exactly what IBIS needs
and has needed since day 1.

IBIS is neither a simulator, nor a simulation methodology.  It is
merely a spec for an electrical model, that is intended to be used in
a SPICE or SPICE-like (analog) simulator.

The very unfortunate thing for us users, is that some of the old SPICE
programs still don't know IBIS.

At work, I use two SPICE programs.  One is generic SPICE with in-house
customizations to know all about the CMOS processes of our fab.  The
other is a popular program with extensions for dozens of other MOS
transistor models.  I *must* use the first program when I want to
simulate something involving the chips we make when I only have models
for the first program.  I *must* use the second program when I want to
simulate something involving external vendor's chips where their SPICE
models are unique to that program, as the majority of external SPICE
models seem to be.  God help me if I have to simulate a signal that
connects between both kinds of chips!

IBIS models only make this worse.  Don't get me wrong; I support the
idea of IBIS models.  But I do not have the means to use an IBIS model
in a simulation; neither of the two SPICE programs I use, knows IBIS.

If I use a newer IBIS-aware signal integrity simulator, it would not
be able to accept at least one of the two types of SPICE models above;
maybe even both.  That is totally unacceptable to me.

If the majority of my models are proprietary SPICE, and occasionally
an IBIS model comes along, and since my environment is already set up
for working with SPICE, I think I am better off (for now) staying with
the SPICE environment.

So considering those increasingly frequent cases where an IC vendor
refuses to show us the SPICE model, it makes a heck of a lot of sense
to translate their IBIS model into a SPICE-usable format.

In fact, I might even expect such a model to be more accurate, if it
is based on measured data.  How often have you gotten a SPICE model
that differed from the measured buffer strength by 300%, or where the
SPICE model completely lacked clamp diodes that were there, or where
all the diodes had zero resistance?  If the IBIS model was created
from measured data, then I should be in much better shape with it,
or a SPICE behavioral model derived from it.

> It seems that something will be lost in going from SPICE Model -> IBIS
> -> SPICE model. My understanding is that (behavioral) IBIS models are
> generally derived from (functional) SPICE models.

Indeed, many are, but they shouldn't be.  We should expect to get
measured IBIS models for anything for which real silicon exists.  IBIS
models derived from SPICE should only be acceptable when the device is
in development and hasn't been built yet.  But, alas, IC vendors are
too stupid or lazy to do this.

> IBIS models and simulators are fine tuned to be faster and easier to use
> for their intended purpose.  This imposes limitations which are not
> realized in the SPICE world (i.e. support for voltage controlled
> multi-stage drivers and the examples you provided).  It seems to me that
> using a SPICE simulator with models derived from IBIS is taking on the
> worst of both worlds: SPICE complexity and run times and IBIS model
> limitations.

What makes SPICE slow, are the SPICE models.  Not the simulator per
se.  SPICE simulates what happens at every single internal node and
device in the structural model, even if they have no effect on the
I/O pin.  IBIS models are faster because they skip all that and
concentrate on just the I/O pin.  SPICE can have behavioral models
too, and they run extremely fast.  Translating an IBIS model into a
behavioral SPICE model should let it run just about as fast as using
the IBIS model directly in an IBIS-aware environment.

Regards,
Andy

---

From: "MARK GAILUS" <[email-masked]>
Date: 27 Oct 1997 12:11:46 -0400

RE>>low budget IBIS tools                    10/27/97

I agree with Fabrizio and Andy.

A free spice2ibis tool does at least as much harm as good by facilitating a
proliferation of IBIS models not derived from or correlated with measurements.

A free ibis2spice tool, on the other hand, would do a great deal towards
making IBIS the defacto format for providing I/O-level device models.

It would also help overcome the difficulties sometimes encountered with
respect to SPICE models supplied in incompatible SPICE dialects, and go a long
way to convince "hardline" SPICE users (perhaps including myself) that
properly constructed IBIS-format models can be more accurate for certain
purposes than many of the available SPICE models.  (It would  be comforting to
know that we could use the familiar and powerful SPICE syntax to modify or
elaborate converted device or package models for any special needs that may
arise in our application.)

A good ibis2spice tool would also assist design/simulation teams who find it
advisable to switch back and forth between narrower SPICE-level simulations
and wider behavioral system-level simulations, by helping make sure that at
least one parameter (the measurement-based buffer model) is held approximately
constant.

Regards

-Mark Gailus
Teradyne Connection Systems

[email-masked]