Subject: RE: Input model with Pullup-/Pulldown-Reference

From: "Muranyi, Arpad" <[email-masked]>
Date: Thu, 8 Nov 2001 08:43:35 -0800

Alex,

Your observation is correct, strictly speaking it doesn't make sense
for an input model type.  I don't remember whether we did it this
way because we wanted to avoid the complications of these ifs and
buts, or whether we didn't think about this case.  However, the
reason these keywords were introduced was to allow independent
referencing of the oullup and power clamp, or pulldown and gnd
clamp IV curves.  When you have an input buffer only, you won't
really need that capability, so you should be able to just use
the [Voltage Range] keyword.  The only problem is that this keyword
assumes that your gnd clamp is at zero volts.  If you had a gnd clamp
at -2V you would have to use the reference keyword, and according
to the rules, all of them, even if there are no pullups and pulldowns.

Even though this should not effect the simulations, it is misleading
to the reader or maker of a model, and should be cleaned up in the
spec.

Thanks,

Arpad Muranyi
Intel Corporation
===================================================================

-----Original Message-----
From: Alexander Loehr [mailto:[email-masked]]
Sent: Thursday, November 08, 2001 1:51 AM
To: [email-masked]
Subject: Input model with Pullup-/Pulldown-Reference

Hi!

I've got an IBIS input model without a [Voltage Range]. Take a look at the
IBIS Specification 3.2:

[Voltage Range] -> Other Notes:
If the [Voltage Range] keyword is not present, then all four of the keywords
described below must be present: [Pullup Reference], [Pulldown Reference],
[POWER Clamp Reference], and [GND Clamp Reference]. If the [Voltage Range]
is present, the other keywords are optional and may or may not be used as
required. It is legal (although redundant) for an optional keyword to
specify the same voltage as specified by the [Voltage Range] keyword.

But it is not possible that an "input" model has [Pullup Reference] and
[Pulldown Reference]. 

Is the IBIS specification correct?

Thanks,
Alex.
-- 
 Alexander Loehr   ZUKEN GmbH           Phone: +49-(0)5251-150622
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