Subject: New EGG?

From: Arpad Muranyi <[email-masked]>
Date: Mon, 08 Jan 96 09:23:00 PST

Happy New Year!

As I am working on enhacements to our internal IBIS tool we are using
around here, I discovered something which might need correction in the
IBIS specification.

In the days of IBIS 1.1, it was assumed that the Ramp data was
obtained with a 50 Ohm load.  In the 2.1 specification, we decided to
add the R_load sub-parameter to this keyword for devices needing a
different load for the dV/dt measurements.

Later, when we defined the sub-parameter R_fixture for the V-t curve
keywords (Rising and Falling Waveform) we did it so that each Waveform
could have their own set of sub-parameters.  We also added the
statement:  "Note that for backwards compatibility, the existing
[Ramp] keyword is still required."

R_load and R_fixture refer to the same load resistor with which the
dV/dt and Waveform measurements are made.  The problem I see here is
that each of the Waveform keywords could potentially have a different
R_fixture value.  If I derived my dV/dt_r and dV/dt_f numbers from
these Waveforms (which is the simplest way of obtaining them), I would
need two independent R_load values for the Ramp sub-parameters.
Currently we have the option for only one.  This forces the model
maker to either make a totally different simulation/measurement for
the Ramp numbers (using only one R_load value for both sub-parameters)
or force the R_fixture numbers to be the same for each Waveform.

I feel we should correct the IBIS specification and allow the use of 
two R_load values, one for each sub-parameter of the Ramp keyword.

I am curious to hear any comments.  If this topic turns serious, this
might be considered an EGG and I will write a BIRD on it later. 
Sincerely,

Arpad Muranyi
Intel Corporation