Subject: SPICEtoIBIS convertor

From: [email-masked]
Date: Wed, 26 Jan 94 17:52:46 EST

Dear IBIS Community:

     I am trying to write a SPICE to IBIS converter that
will be of use to the IBIS Community (IC) and prospective members
of the IC.   I am writing to you to solicit opinions and other 
information that might be helpful in making the product useful 
to the largest possible audience.   

     To begin with, my understanding is that there is not yet a written 
specification for the converter.    Therefore, let me present my
own mini-specification and a couple of concerns I have:

                      SPICEtoIBIS mini-specification
                      ------------------------------

     Purpose:  SPICEtoIBIS accepts a commented SPICE input deck;
               runs the necessary SPICE simulations to generate
               Pulldown, Pullup, GND_clamp, POWER_clamp, and Ramp
               tables with typ, min and max columns using the
               NOTES ON DATA DERIVATION METHOD section from
               version 1.1; and uses the comments in the SPICE
               deck and the SPICE output data to generate a
               syntactically-correct IBIS 1.1 model.   [Pin]
               information will be entered at the beginning of
               the SPICE deck using standard IBIS syntax except
               that an extra column is added to any line that
               describes a pin to be included in the IBIS model,
               and of course all lines are preceded by the SPICE
               comment character.   Additionally, the first line
               of the input deck must be a comment line with
               BIPOLAR or CMOS somewhere on it.

                     ---------------------------------

      This seems pretty straightforward, but I have some concerns
about it and would greatly appreciate any comments, help, etc regarding
this mini-spec and/or the following concerns:

      1) Some Si vendors use .TNOM and separate .MODEL cards for each
         temperature simulated, and some may use one .MODEL for all
         temperatures and a .TEMP card alone.  On a related note,
         any vendor that does use .TNOM probably does not use 50 and
         100 degrees C models.  Is the converter required to figure
         out which technique is being used and kludge a reasonable
         .TNOM and .TEMP for whatever model is given, or is the vendor
         supposed to go to the bother of generating new models?

      2) What about BiCMOS devices?  (sorry if this is a dumb question...)

      3) Is it OK to use a constant step size in the tables, or is
         it really desirable to minimize the number of entries?

      4) Are there other features required?

     Ignoring the concerns listed above I can put something 
with a nominal amount of error-checking together in fairly short order,
but I hope to be able to provide you with a robust, general-purpose
tool, so I would greatly appreciate any comments and or suggestions
that you may have.   If anyone can send me examples of their SPICE
simulation files and/or associated IBIS models, this would be a great
help.  I assume that a wide variety of approaches are used,
and seeing as many examples as possible will help me to make a more
general-purpose tool.

     Thanks in advance for any help you can provide!

     Steve Lipa
     [email-masked]         

     919-515-3947