Subject: RE: [IBIS] Question on IBIS Version 4.0
From: Muranyi, Arpad (arpad.muranyi@intel.com)
Date: Mon Nov 04 2002 - 08:30:25 PST
Elena,
The two statements about the first point and the time correlation
are not related. The time correlation doesn't mean that all curves
should have the same first time value in the tables. It means that
they should be all generated from a stimulus that triggered the
buffer at the same time for each of the Vt tables.
Independent from that, one table could start at 1 ns, the other at
1.1 ns and the third at 0.9 ns, etc... if you please. (I don't know
why you would want to do this, but I believe the spec allows this).
The real question is: what are the tools going to do with this?
Some tools automatically normalize the curves to zero time, others
will not. If the curves are simulated at the time they are given,
that means that the buffer in the simulation will have a delay of
the amount where the Vt curves begin. This could mean that the
buffer can get over clocked very easily if your stimulus switches
faster than the amount of time that marks the first points of the
Vt tables.
Arpad Muranyi
Intel Corporation
====================================================================
-----Original Message-----
From: Elena Gutman [mailto:egutman@emc.com]
Sent: Monday, November 04, 2002 5:49 AM
To: ibis@eda.org
Subject: [IBIS] Question on IBIS Version 4.0
Hello,
There is a statement in the IBIS spec which is in 'Section 6',
named 'MODEL STATEMENT' on 'Keywords: [Rising Waveforms],[Falling Waveforms]'
The sentence carries over from the first revision of the IBIS to the
latest one IBIS Version 4.0. This sentence claims that -
"The first value in the time column need not be '0'."
Could any one explain to us what it means, and let us know whether our
interpretation of this sentence or section (which is written below)
is correct or incorrect.
Our interpretation of that is very simple. According to the latest IBIS Version 4.0,
'the data in all of the waveform tables should be time correlated, meaning,the edge
data in each of the tables (F and R) should be entered with respect to a single point
in time ...and so on.. '
In other words, the first line of each waveform table should start at the same point
in time, therefore if the Rising waveform starts at 1ns, so too should the Falling
waveform. With this comes the assumption that they can be of a value other than '0',
but MUST, at all times, be of the same value.
In order for us to fully understand whether we are having a tool issue or a verdor issue,
your assistance with the interpretation of the above statement in the IBIS spec
would be greatly appreciated.
Thanks,
-------------------------------------------------------
Elena Gutman * EMC Corporation * email: egutman@emc.com
*
Tel (508) 435-1000 ext. 44766
Fax (508) 497-8741
*
176 South Street
Hopkinton, MA 01748-0913
*
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