RE: S2ibis2 -- inputs with pull-up resistors, bi-directionals, Rising Waveforms, Falling Waveforms, etc.

Hello,

I need some help clarifying the creation of models in IBIS.

1. Inputs with pull-up resistors?
Are these treated in any special way? (ie: different than that of a
normal input pin?)

2. Bi-directionals?
I have a pad structure that has the following nodes:

Pad (the output)
Oen (ouput enable)
In (feeds the output when output enable is asserted, and Pad functions
as an output)
Cin (feeds the core when output enable is deasserted, and Pad
functions as an input)

What is the proper way of setting this up in s2ibis2?

3. Rising and Falling Waveforms.
I understand that these are supposed to describe the rising and
falling edge waveforms of a driver, yet they are not required. There
is also a note in the IBISv2.1 specification that states: "...A
maximum of 100 waveform tables are allowed per model. Note that for
backwards compatibility, the existing [Ramp] keyword is still
required. The data in the waveform table is taken with the effects of
the C_comp parameter included..."

From this, I was wondering, what would having 100 waveform tables be
used for? Further, are the Rising and Falling Waveforms somehow a -
replacement - for the [Ramp] keyword? Are the Rising and Falling
waveforms usually generated in the lab at the bench, or can they be
simulated? When are they required, if at all?

4. Analog and Digital VDD's and VSS's.
In the spice netlists of the files that I am dealing with, I often
multiple VDD's, for example, VDDac, and VDDdc, which are used to
power up separately the I/O ring and the core. Has anyone else out
there had to deal with multiple VDD's like this? (I'm not talking
about multiple VDD's such as 3.3 and 5 V, such that can be solved
using pin mapping)

5. Stimulus input voltage risetime and falltimes
How are these parameters used? And for what curves are they used
for?

Clarification of any of the above questions (1-5) would be greatly
appreciated,
Thanx!

Best Regards,
Roland

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*Roland Chang | email: roland@sfu.ca
          *
*Simon Fraser University | OR
                     *
*School of Engineering Science | chang@pmc-sierra.bc.ca
 *
*3rd year Computer Engineering Option |
                               *
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Received on Wed May 28 17:24:17 1997