Subject: 3-state pullup table generation by s2ibis2 0.91BETA

From: [email-masked] (Hoang Nguyen)
Date: Tue, 11 Feb 97 11:35:26 EST

Hello IBIS users:

We at Mitsubishi have evaluated the new version of s2ibis2 v1.0,
and we're quite please with the new features and good documentation.
Thank you to the IBIS developers at NCSU.

A couple of tests were run with s2ibis2 version 1.0 and 0.91BETA on the
same device.  We observed the results and thought that there is a problem
in 0.91BETA version regarding pullup table generation for 3-state pin.

To generate the Pullup table for 3-state pin, 0.91BETA version subtracts
the pullup disable curve from the pullup enable curve for the entire
sweep range [-Vcc to 2*Vcc].  While the correct subtraction should be
in the pullup disable range [Vcc to 2*Vcc], which is the same as the
Power Clamp range.  Such operation executes properly in the new version 1.0.

We had provided numerous models generated by 0.91BETA version to customers. 
I wonder if other IBIS users and model providers experience a similar problem.
Although 0.91BETA is just a beta version, I feel that all 3-state models 
generated by 0.91BETA should be re-run using the latest s2ibis2 version 1.0
to meet IBIS SPEC. This may take a while if you have to re-do a lot of models.
I will be glad to hear your ideas/comments on this, as well as how servere the 
impact of the bug on IBIS simulators you're using.

Best regards,

Hoang Nguyen

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From: [email-masked] (Raj Raghuram)
Date: Tue, 11 Feb 1997 11:57:14 -0800

This is in reply to Hoang's comments on s2ibis v1.0. In my earlier job (at 
National) we used s2ibis to generate version 1 IBIS models for a number of 
tristate devices. I do not remember the version number of s2ibis. I suspect it
is an earlier version as we did this in Jan. 1995. We did find a problem with
s2ibis and corrected it.

The problem was exactly what you have mentioned. There is an error in 
subtracting the curves with the output enabled and the output floated.

************************************************************************
Raj Raghuram                                                  
Applied Simulation Technology,                 
2188 Bering Drive,                               
San Jose, CA-95131.                              
Tel: (408) 434-0967 ext.101
Fax: (408) 434-1003
e-mail: [email-masked]
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