Subject: WaVEFORMS FOR BIRD12.1

From: "Hobbs, Will" <[email-masked]>
Date: Tue, 10 May 94 22:51:57 PDT

Bob,

          If I understand your question, for the Vcc/2 waveform,
          wouldn't (4) be the only valid option?  Option (2) would
          also be correct if the load were 100 ohms each, for a total
          Thevenin equivalent of 50 ohms.  Or am I out in left field?

          Will

To Jon Powell, Arpad Muranyi, and IBIS Committee:

This is an open implementation preference question based on the waveforms
you have sent.  In particular, refer to Jon Powell's "Synchronizing
Measure AC Waveforms ... " document recently sent which illustrates
the synchronization of rising and falling waveforms measured into 
50 Ohm loads at 0, 2.5 and 5V.

How do you "blend" certain data combinations that would be allowed via the
BIRD12 [Rising waveform] and [Falling waveform] mechanisms?  And which
form would you prefer seeing?

Cases -->             (1)   (2)   (3)   (4)

Low_To_High:
  50 Ohm to Vcc              *     *  
  50 Ohm to Vcc/2                  *     *
  50 Ohm to GND        *     *     *

High_To_Low:
  50 Ohm to Vcc        *     *     *    
  50 Ohm to Vcc/2                  *     *
  50 Ohm to GND              *     * 

Note, Case (1) corresponds to the [Ramp] specification conditions in IBIS
Version 1.1.

Bob Ross
Interconnectix, Inc.

---

From: [email-masked] ( Bob Ross)
Date: Wed, 11 May 94 09:02:59 PDT

Will, 

I see the confusion.  What I meant was that for Case (2), you would
provide 4 waveforms for each of the R_fixture and V_fixture combinations
listed.  In Case (3), 6 waveforms would be provided.  Jon's document
showed six waveforms, all of which could be included in the IBIS [Model]
description.  I have no objection to having as much waveform characterization
information as possible provided.  It becomes a simulator vendor's problem
to figure out how best to use this information (or to choose what information
not to use).   I raised the question to see if there were any preferred
combinations, and any preferred ways of dealing with multiple sets of data.

Bob