Re: Re[2]: IBIS modeling questions

Will,

This is only a personal opinion, but for what it is worth, I think it would be
equitable for someone to provide an executable on a platform for which you have
none, in exchange for the license fee for the source code. (I'm not
volunteering.) If you were concerned that you might not get the executable in a
timely manner, you could at least offer to refund the license fee on recepit
and approval of the executable.

Fred

Begin forwarded message:

Date: Thu, 09 Nov 95 16:27:00 PST
From: Will Hobbs <Will_Hobbs@ccm.jf.intel.com>
Message-ID: <Thu, 09 Nov 95 16:32:07 PST_9@ccm.jf.intel.com>
To: fvance@firepower.com, grege@chensys.com
cc: ibis@vhdl.org
Subject: 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
afee. There are many companies who have licensed the code, and we are in
theprocess of porting it to various O/S and platforms. When that work is done,
theresulting 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 outto
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
thefull range is provided. It might depend on a simulator's interpretation
of the
IBIS specification. If I remember correctly, using the full range is optionalin
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 availableto you. Since
you seem to have some experience with C compiling, you might be the rightperson
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
dependentfunctions to control a conductance to Vdd, simulating a pull-up
switchand one
to Gnd simulating a pull-down switch. The independent variable controllingthe
dependent conductance functions would be the voltage at the driver's outputpad.
Both conductance switches also need to be dependent on the pin's logicstate and
need to make a transition between states at a controlled rate usingthe dV/dt
information in the IBIS. The state transition would have to occurbased 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
toknow issues and limitations involved with behavioral model simulations.
It may
be difficult to discuss IBIS models independent of a specific simulator,
butmight be interesting to try.

Regards,

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

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Subject: Re: IBIS modeling questions
To: grege@chensys.com (Greg Edlund)
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