Re[2]: IBIS modeling questions

Text item:

Fred, Greg,

Sorry to be a bearer of bad news, but the source code must be licensed, for a
fee. There are many companies who have licensed the code, and we are in the
process of porting it to various O/S and platforms. When that work is done, the
resulting object code will be made freely available on vhdl.org. If you do want
to license the parser, here are the details:

There are three options for licensing the IBIS Golden Parser source code,
V2.1, depending on your membership status in the IBIS committee of EIA:

1) If you are a current member of the IBIS committee, you can license the
parser source for an additional $250.00
2) If you are not a member, but would like to be, you can join the committee
and license the parser source for a total of $750
3) If you are not a member, and do not wish to become a member, you can
license the source for $500.

In any case, submit a request to:

     EIA
     2500 Wilson Blvd.
     Arlington, VA 22201
     (703) 907-7545 (phone)
     (703) 907-7501 (fax)
     
Enclose a check in the appropriate amount made out to EIA. EIA will take
care of distributing the source.

Regards,

Will Hobbs,
Chair, EIA IBIS Committee
Intel Corp.

Hi Greg,

You wrote:

>To: ibis@vhdl.org
>From: grege@chensys.com (Greg Edlund)
>Subject: IBIS modeling questions
>
>Anybody care to take a stab at these?
>

I'll give it a try.

>1. I was discussing IBIS model support with one of
> our IC vendors, and they raised a concern about
> ESD diode SPICE models not being accurate at
> -5 V and + 10 V. Any clues about how to get
> around this without setting up a test lab? Why
> do you need such a wide range in the first place,
> since nobody operates out there?

I think that some simulators use the last couple of points to extrapolate out
to infinity or some asymptotic value, so if your data is not available
over the
full range, you can probably do the same. Maybe it doesn't matter whether the
full range is provided. It might depend on a simulator's interpretation
of the
IBIS specification. If I remember correctly, using the full range is optional
in the latest IBIS revision. (Someone help me here.)

>2. When will s2ibis 2.0 be available on Windows?
> Actually, I'd be happy with DOS, but that's
> probably not in the plan...
>

I believe someone would be glad to make the source code available
to you. Since
you seem to have some experience with C compiling, you might be the right
person to create the DOS/Windows executable and upload it to ibis@vhdl.org.

>3. Has anybody written a "theory of operations"
> paper on behavioral simulators? For instance, if
> I have a simple behavioral driver model (no ESD
> diodes, no package) driving a 50 Ohm transmission
> line terminated at the far end into 50 Ohms, how
> do I calculate the current and voltage vs. time at
> the output of the driver? At the far end? This
> must be an easy problem to solve. I'd like to
> write a little C program to do this so I can better
> understand IBIS and critically compare it to SPICE.
> (For the sake of accuracy in system design issues,
> not so I can write another simulator!)
>

Maybe, I can't really say.

I believe the way to approach this is to use piece-wise linear dependent
functions to control a conductance to Vdd, simulating a pull-up switch
and one
to Gnd simulating a pull-down switch. The independent variable controlling
the
dependent conductance functions would be the voltage at the driver's output
pad. Both conductance switches also need to be dependent on the pin's logic
state and need to make a transition between states at a controlled rate using
the dV/dt information in the IBIS. The state transition would have to occur
based on some threshold value and the buffer's input level.

Sounds simple, only the details get in the way.

>4. Has anybody thought about organizing an IBIS
> users group and mailing list?
>

This is it, I think. I would be happy to discuss the "theory of operations"
of
behavioral simulators in more detail.

I agree that for the "sake of accuracy in system design issues" it is good to
know issues and limitations involved with behavioral model simulations.
It may
be difficult to discuss IBIS models independent of a specific simulator, but
might be interesting to try.

Regards,

Fred Vance
FirePower Systems, Inc.
(415) 462-3055 Phone
(415) 462-3051 Fax

Text item: External Message Header

The following mail header is for administrative use
and may be ignored unless there are problems.

***IF THERE ARE PROBLEMS SAVE THESE HEADERS***.

Cc: ibis@vhdl.org
Subject: Re: IBIS modeling questions
To: grege@chensys.com (Greg Edlund)
Received: by NeXT Mailer (1.99.1)
Received: by NeXT.Mailer (1.99.1)
Date: Thu, 9 Nov 95 12:44:34 -0800
Received: by protocol.FirePower.COM (NX5.67d/NX3.0X)
     id AA02374; Thu, 9 Nov 95 12:44:34 -0800
Message-Id: <199511092044.MAA17874@freedom.firepower.com>
From: Fred Vance <fvance@firepower.com>
Received: from protocol.FirePower.COM (protocol.firepower.com [198.4.104.87]) by
 freedom.firepower.com (8.7.1/8.7.1) with SMTP id MAA17874; Thu, 9 Nov 1995 12:4
4:36 -0800 (PST)
Received: from freedom.firepower.com (freedom.firepower.com [198.4.104.3]) by fi
repower.com (8.7.1/8.7.1) with ESMTP id MAA21114; Thu, 9 Nov 1995 12:43:21 -0800
 (PST)
Received: from firepower.com (freespeech.firepower.com) by vhdl.vhdl.org (4.1/SM
I-4.1/BARRNet)
     id AA27155; Thu, 9 Nov 95 12:52:13 PST
Received: from vhdl.vhdl.org by aurora.intel.com (5.65/10.0i); Thu, 9 Nov 95 13:
40:37 -0800
Received: from aurora.intel.com by ichips.intel.com (5.64+/10.0i); Thu, 9 Nov 95
 13:42:26 -0800
Received: from ichips.intel.com by relay.jf.intel.com with smtp
     (Smail3.1.28.1 #2) id m0tDejt-000twnC; Thu, 9 Nov 95 13:42 PST
Received on Thu Nov 9 16:41:56 1995