Subject: bird2.1

From: [email-masked] (Jon Powell)
Date: Wed, 16 Feb 94 16:01:34 PST

Hey guys,

Here is my long promised try at bird 2.1. I had to make more
change suggestions than I wanted to but it seems that this is
a good time to get this stuff out and discussed before we make
the new parser etc.

                 Buffer Issue Resolution Document  (BIRD)

BIRD ID#:      2.1
ISSUE TITLE:   Requiring VIH VIL thresholds for input devices
REQUESTOR:     Jon Powell, Quad Desgin

DATE SUBMITTED:                       10/4/93 rev 2.1 2/16/94
DATE ACCEPTED BY IBIS OPEN FORUM:     {will be filled in when accepted}

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STATEMENT OF THE ISSUE:

	The V1.1 IBIS specification does not require the presence of input
	thresholds on input devices. This allows data-generators to omit
	thresholds and still create "IBIS LEGAL" models. Input devices with
	no stated digital logic input thresholds would not allow for the calculation
	of digital pin-to-pin delays which is a very important quantity to many
	potential users. Requiring a low and high threshold
	for all input devices is therefor a reasonable requirement that adds
	information without creating undo restrictions.

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STATEMENT OF THE RESOLVED SPECIFICATIONS:

modify the [Model] statement to take into account different devices separate
from device technology.

Model_type       Input Output I/O analog_load                | list one only
Model_technology TTL CMOS ECL GAL OTHER                      | list one only
Model_structure  Tri-state Open-Drain Open-Collector Normal  | list one only

Devices of type Input and I/O would give a warning if Vih and Vil are not specified
and a default of .8 and 2.0 (low high respectively) would be generated.

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

	There are devices that are not Input or Outputs and are not handled by
	our current set of model types. For instance:

	Termination Resistor Packs
	Termination Diode Packs
	Descrete 2 port devices

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ANY OTHER BACKGROUND INFORMATION:

      {These documents will be archived, so use this section to carry any detail
       that is not essential to the previous section, but should not be lost.}

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