RE: [IBIS] Question regarding V-t tables

Arpad,

If multiple waveforms are given for the same loading condition how would a simulator use them? One approach might be to simply average them in some way. I see no use for such data. Of course a real part might respond differently to different data patterns, but that means you have to go way back in the architecture of the part to extract the reasons for that behavior and model them. The IBIS structure certainly does not allow for any such modeling. I suggest that if something that sophisticated is actually needed then you should use VHDL-AMS or SPICE models.

Chris

-----Original Message-----
From: owner-ibis@eda.org [mailto:owner-ibis@eda.org] On Behalf Of Muranyi, Arpad
Sent: Wednesday, September 08, 2004 11:30 AM
To: ibis@eda.org
Subject: [IBIS] Question regarding V-t tables

All,

I just realized something regarding the V-t tables in IBIS that raises a question in my mind.

The spec says that we can have up to 100 V-t tables. It doesn't say anything on how Vfixture and Rfixture should be selected for these to make a good model.

Many simulators can only support the first four tables, but I am aware of some which can make use of all of them. As far as I know, the algorithms which make use of all of them assume that the additional tables generated with the various Rfixture and Vfixture values provide a better understanding for how the buffer reacts to various loading conditions.

What I would like to find out is this: What would happen if an IBIS file had multiple V-t tables with repeated Rfixture and Vfixture parameters, but different waveform shapes? (This ***CAN*** happen nowadays with advanced buffers which exhibit data pattern dependent behaviors). Obviously, given the current spec, the tool wouldn't know when to use which table. Would this be a good reason to write another BIRD for some additional subparameters for the V-t tables?

Arpad
=======================================================================

-----------------------------------------------------------------
|For help or to subscribe/unsubscribe, email majordomo@eda.org with the
|appropriate command message(s) in the body:
|
| help
| subscribe ibis <optional e-mail address, if different>
| subscribe ibis-users <optional e-mail address, if different>
| unsubscribe ibis <optional e-mail address, if different>
| unsubscribe ibis-users <optional e-mail address, if different>
|
|or email a request to ibis-request@eda.org.
|
|IBIS reflector archives exist under:
|
| http://www.eda.org/pub/ibis/email_archive/ Recent
| http://www.eda.org/pub/ibis/users_archive/ Recent
| http://www.eda.org/pub/ibis/email/ E-mail since 1993
-----------------------------------------------------------------
|For help or to subscribe/unsubscribe, email majordomo@eda.org
|with the appropriate command message(s) in the body:
|
| help
| subscribe ibis <optional e-mail address, if different>
| subscribe ibis-users <optional e-mail address, if different>
| unsubscribe ibis <optional e-mail address, if different>
| unsubscribe ibis-users <optional e-mail address, if different>
|
|or email a request to ibis-request@eda.org.
|
|IBIS reflector archives exist under:
|
| http://www.eda.org/pub/ibis/email_archive/ Recent
| http://www.eda.org/pub/ibis/users_archive/ Recent
| http://www.eda.org/pub/ibis/email/ E-mail since 1993
Received on Wed Sep 8 17:07:45 2004