Subject: Questions about BIRD39 - SPECIFICATION ENHANCEMENT

From: [email-masked] (Dileep Divekar)
Date: Wed, 6 Nov 1996 09:07:43 +0800

I have some questions about BIRD39 - SPECIFICATION ENHANCEMENT.
1)I do not understand the intended use of the Vinh+,Vinh-,
Vinl+ and Vinl- subparameters. Can some one offer more explanation?
2)My understanding was that IBIS is used for analyzing signal
integrity effects for rising and falling EDGES. There is no notion
of a pulse or pulse width anywhere in the specification.
Since there is really no output vs. input information, one can
arbitrarily assume the times at which the output transitions can
start and hence I do not know how the Pulse_high, Pulse_low and
Pulse_time subparameters are to be used.
Thank you for your help.
Dileep
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Dileep Divekar
Applied Simulation Technology, Inc.
2188 Bering Drive
San Jose, CA 95131

Phone - (408)-434-0967 x 100
Fax   - (408)-434-1003
Email - [email-masked]
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From: [email-masked] ( Bob Ross)
Date: Wed, 6 Nov 96 15:27 PST

Dileep:

Good questions.

(1)  One specific example is the 74XXX132 device with
Schmitt trigger (hysteresis) input specification.  The
high and low state threshold points are specified within
a tolerance range.  In general, ASIC devices with hysteresis
inputs could also benefit from this Specification addition.
The proposed Specification addition would allow us more
precision in allocating timing paths.  Currently with
only Vinh and Vinl, we have only a very crude way of
approximating hysteresis behavior without any real
tolerance mechanism.

(2)  I also would like feedback on the need and appropriateness
of this noise rejection inclusion and how it might be used.
The specification is designed to allow simulators to optionally
set up tests and trap on glitches at the input to test noise
immunity.  So an input that is at a low state may see a 
glitch due to timing or cross talk tolerances that cause it
to momentarily exceed the Vinl value.  As long as the
input remains below Pulse_high and also returns to a value
below Vinl, within Pulse_time of the first crossing, the input
with such a noise immunity specification is considered to have
passed.  (This is a first order approximation of a more detailed
pulse-width versus pulse amplitude characteristic and is intended
to help flag possible weaknesses.)  The Pulse_low value operates
in a similar manner relative to Vinh when the input is in the
high state.

Bob Ross
Interconnectix

> Date: Wed, 6 Nov 1996 09:07:43 +0800
> From: [email-masked] (Dileep Divekar)
> Message-Id: <[email-masked]>
> To: [email-masked]
> Subject: Questions about BIRD39 - SPECIFICATION ENHANCEMENT
> Cc: [email-masked]