Subject: R_fixture and R_ref

From: Paul Gregory <[email-masked]>
Date: Thu, 21 Jan 1999 12:14:02 MST

In an IBIS model, if R_ref is not specified, is R_fixture used
as a default value?  I know that this may be tool specific, but
I hope that there is a common answer.

Of course, the common answer may be to *always* specify R_ref.

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From: "Beal, Weston" <[email-masked]>
Date: Thu, 21 Jan 1999 13:29:14 -0600

Paul,

Although R_ref and R_fixture get put in the same topology in respect to the
driver, the use of these to parameters is very different, so I would hope
that no simulator assumes one from the other.  R_ref is for board level
timing adjustment while R_fixture partially defines the environment in which
the rising and falling waveforms were measured.  I good simulator could
scale the time waveforms if the resistance of the simulation environment is
different than the measurement environment.

Regards,
Weston