RE: [IBIS-Users] ODT topics

From: Muranyi, Arpad <arpad.muranyi_at_.....>
Date: Mon Apr 04 2005 - 09:51:09 PDT
Andy,

(I got two of these messages).

You are making a good point, but the way I understood
this story was that if you didn't define those optional
clamp reference nodes, the current was automatically
coming out of the pullup and pulldown reference nodes,
just as if the clamp reference would have been shorted 
to them.  Now, in the earlier version of HSPICE there
was a bug in this, but I thought that was fixed a long
time ago, though I didn't check it lately.  I got too
used to defining all nodes every time I use it...

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

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Andrew Ingraham
Sent: Saturday, April 02, 2005 5:34 AM
To: ibis-users@eda.org
Subject: Re: [IBIS-Users] ODT topics

Hmmm, my mail doesn't seem to be reaching eda.org.  Here is try # 3:

> "My question would be: what are simulators (e.g. HSPICE) really doing with
> IBIS models ...

> The clamp I-V tables are always present in the simulation, and
> the pullup and pulldown I-V tables are switched on/off as the
> buffer is driving high/low.  The end result is that the currents
> of the pullup or pulldown I-V tables are added together with
> the clamps.

Well actually, ...

Sorry to nit-pick, but in HSPICE the clamps are not necessarily always
there.  The end-user who puts an IBIS model in his simulation needs to make
sure to include ALL the optional element nodes.  If he leaves the optional
nodes out, HSPICE has this nasty feature (it is really intended as a
feature, not a bug) that the clamp I-V tables are omitted.

Once those nodes are included in the netlist, then Arpad's statement above
is correct.

Regards,
Andy

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Received on Mon Apr 4 09:51:12 2005

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