RE: [IBIS-Users] IBIS File Help

Hello Eric,

It could be bad Rising/Falling table data, with bad DC values. But then
IBISCHK should throw out an error. So that can't be it.

Do the Rising/Falling tables have an exceedingly long leading delay? If
that's the case. Then the model might be over-clocked and the simulator
might never reach its final DC level. Try running the simulation at a
lower data rate. If there is a large initial delay, then that probably
indicates a bad model. Most simulators can remove this initial delay,
but it would be better if that delay wasn't in the model in the first
place (because initial delay removal algorithms can never be guaranteed
to always produce a "correct" model).

If that doesn't help, I would suggest contacting customer support for
the Vendor of the simulator Vendor that produces the wrong DC levels.

Cary Mandel
Mentor Graphics

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of Eric Monteiro
Sent: 04 February 2010 18:22
To: ibis-users@eda.org
Subject: [IBIS-Users] IBIS File Help

Hello

I have generated an IBIS file for an ECL open collector driver. When I
do the IBISCKH, I get 0 warnings and 0 errors. However, when I try to
use the model in a certain tool, the output swings are not as expected.

1) My [Rising Waveform] and [Falling Waveform] shows the wave go from
1.7 to 3.3 volts.
2) IBIS CHK comes back clean, so my DC tables must agree that those are
the end points.
3) I place the part into the tool, terminate the open collector to the
same R_fixture and V_fixture in the IBIS file
4) I run at the correct data rate, and the output comes out at 1.7 to
2.2 volts...

However in a different simulator I get 1.7 to 3.3 with the same test
bench... BUT if I delete the [Rising Waveform] and [Falling Waveform]
data, the two simulators agree.

Has anyone seen this with thier models?

Does this mean there is an issue with my IBIS files DC data? I am quite
puzzled on this one.

(The file is quite large, I can send it to anyone interested in this
issue)

Best Regards,
Eric

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