[ibis-macro] Re: Important question, please reply!

  • From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>
  • To: <ibis-macro@xxxxxxxxxxxxx>
  • Date: Wed, 2 Nov 2005 13:46:09 -0800

Bob,

I have thought about that possibility myself.
However, as they say, if it can happen it will
happen, I believe we cannot enforce that the
table will always be long enough to cover all
possibilitites.  And if it is not long enough,
my model has to do something about it.  I don't
see a way around that in my code.  It will 
either do HE or SE or I can even put code in
there that would stop the simulator, or hang
the system (infinite loop), but I can't do
nothing...

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

-----Original Message-----
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] 
On Behalf Of Bob Ross
Sent: Tuesday, November 01, 2005 4:45 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: Important question, please reply!

Arpad:

After thinking about the discussion and problem, I have
some more thoughts.

Why do we need it defined outside the range?

Like with IBIS models, the burden should fall on the
model developer to provide the data over a reasonable
range of operation.  The tool using the macro library
will implement the macros according to their actual
operation.  Some tools will do HE,, others will do SE.

This would occur whether or not the macro is officially
defined for one mode and a non-compliant vendor still
uses the macro approach.

So, I would now leave it as undefined, and encourage
that the data cover a reaonable range of operation,
as defined in the IBIS Spec.   (HE of time data seems
seems to automatically occur in all tools to the
point that truncating the time data is a good
practice.)

Bob


Muranyi, Arpad wrote:

> All,
> 
> I would like to get everyone's input on this question,
> because we could not decide in today's meeting which
> way the library should implement the PWL sources.  The
> difficulty in making a decision is due the conflict of
> various aspirations:  tool compatibility (everyone seems
> to be doing something different, even multiple tools of
> the same company are some times different), maximum
> flexibility, and consistency.
> 
> 
> 1)  What should the PWL sources do when the input is
> outside the range of the table definition?  The options
> I can think of are:
>  
> a) Repeat the first or last points, which amounts to a
>    horizontal extrapolation (HE), or
> b) use the first and last slopes and extrapolate with that,
>    which I call slope extrapolation (SE), or
> c) use HE for PWL-s in which the independent axis is time,
>    and use SE for PWL-s in which the independent axis is 
>    voltage or current
> d) add a parameter to the model and let the user choose.
> 
> 
> 
> 2)  The second question is regarding the event triggered
> PWL sources.  Does anyone else besides Cadence's have such 
> PWL sources?  If so, could you please describe it to me so
> I could choose an implementation that matches most tools.
> 
> 
> You response would be very important.  If you feel
> uncomfortable to reply publicly, please send an email 
> to me directly.  I know we have at lest 10 companies
> on this list, so I would like to get at least 10
> responses.  (I hope I am not going to get 11 or more
> different answers, though :-)
>  
> Thanks,
>  
> Arpad
> ==========================================================
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-- 
Bob Ross
Teraspeed Consulting Group LLC     Teraspeed Labs
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