IBIS List Email Archive: IBIS BIRD59.2

From: Bob Ross <bob_ross@mentorg.com>
Date: Fri Aug 20 1999 - 13:25:53 PDT

To IBIS Committee:

BIRD59.2 is issued with some minor editorial changes made at the August 20,
1999 Meeting where it was approved.

The minor changes are show with |** lines.

Bob Ross
Mentor Graphics

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BIRD ID#: 59.2
ISSUE TITLE: Model Spec Diagrams
REQUESTER: Bob Ross, Mentor Graphics
DATE SUBMITTED: August 3, 1999, August 6, 1999, August 20, 1999
DATE ACCEPTED BY IBIS OPEN FORUM: August 20, 1999

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STATEMENT OF THE ISSUE:

The need to illustrate some [Model Spec] subparameters was raised in letter
ballot responses to SP-4557.

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STATEMENT OF THE RESOLVED SPECIFICATIONS:

The [Model Spec] keyword is presented with added diagrams. Added clarifying
statement in the text are shown by |* lines. Included is a reference to
Schmitt trigger inputs, and static overshoot definition.

Replace the existing [Model Spec] keyword with the text below:

|=============================================================================
| Keyword: [Model Spec]
| Required: No
| Sub-Params: Vinh, Vinl, Vinh+, Vinh-, Vinl+, Vinl-, S_overshoot_high,
| S_overshoot_low, D_overshoot_high, D_overshoot_low,
| D_overshoot_time, Pulse_high, Pulse_low, Pulse_time, Vmeas
| Description: The [Model Spec] keyword defines four columns under which
| specification subparameters are defined.
|
| The following subparameters are defined:
| Vinh Input voltage threshold high
| Vinl Input voltage threshold low
| Vinh+ Hysteresis threshold high max Vt+
| Vinh- Hysteresis threshold high min Vt+
| Vinl+ Hysteresis threshold low max Vt-
| Vinl- Hysteresis threshold low min Vt-
| S_overshoot_high Static overshoot high voltage
| S_overshoot_low Static overshoot low voltage
| D_overshoot_high Dynamic overshoot high voltage
| D_overshoot_low Dynamic overshoot low voltage
| D_overshoot_time Dynamic overshoot time
| Pulse_high Pulse immunity high voltage
| Pulse_low Pulse immunity low voltage
| Pulse_time Pulse immunity time
| Vmeas Measurement voltage for timing measurements
|
| Usage Rules: [Model Spec] must follow all other subparameters under the
| [Model] keyword.
|
| For each subparameter contained in the first column, the
| remaining three hold its typical, minimum and maximum values.
| The entries of typical, minimum and maximum must be placed on
| a single line and must be separated by at least one white
| space or tab character. All four columns are required under
| the [Model Spec] keyword. However, data is required only in
| the typical column. If minimum and/or maximum values are not
| available, the reserved word "NA" must be used indicating the
| typical value by default.
|
| The minimum and maximum values are used for specifications
| subparameter values that may track the min and max operation
| conditions of the [Model]. Usually it is related to the
| Voltage Range settings.
|

Remove this statement and replace it with the reworded statement below:

| Unless noted below, each subparameter does not require having
| any other subparameter.

|* Unless noted below, no subparameter requires having present
|* any other subparameter.

End of rewording change

|
| Vinh, Vinl rules:
|
| The threshold subparameter lines provide additional min and
| max column values, if needed. The typ column values are still
| required and would be expected to override the Vinh and Vinl
| subparameter values specified elsewhere. Note: the syntax
| rule that require inserting Vinh and Vinl under models remains
| unchanged even if the values are defined under the [Model
| Spec] keyword.
|

Remove this paragraph in response to Intel Comment 6

| To mimic a hysteresis effect, the values of Vinh and Vinl may
| be interchanged such that the Vinl value is larger than the
| Vinh value. However, simulators may process this information
| differently or report an error.
|

End of removed paragraph

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

Diagrams are added to clarify meanings and also to illustrate switching
points for the Vinl-, Vinl+, Vinh-, and Vinh+ hysteresis subparameters and for
the pulse immunity subparameters Pulse_high, Pulse_low, and Pulse_time.

Diagrams also show regions where the receiver waveform passes and fails
the overshoot constraints based on S_overshoot_high, S_overshoot_low,
D_overshoot_high, D_overshoot_low, and D_overshoot_time subparameters.

A short explaination is added for the static overshoot parameters to respond
to Intel's comment below.

BIRD59.1 is issued in response to comments at the August 6, 1999 IBIS Meetings
where BIRD59 was introduced. Also some editorial corrections are made in
the diagram for hysteresis thresholds.

A clarification statement is made to also refer to the commonly used term
in ASIC data books referring to Schmitt trigger input. The alternatives
discussed included adding a table, doing another switching diagram, and
provide a more comprehensive definition. We opted for a minimal amount of
work to avoid getting bogged down in producing a larger statement (with
possible errors).

Also, as a result of this discussion and a reflector comment on BIRD59, the
switching region is added to the hystersis diagram.

Also, one paragraph is deleted in response to Intel letter ballot comment 6
for this keyword shown in the Any Other Background Information section below.

BIRD59.2 shows the addition of "DC" made at the August 20, 1999 meeting to
further clarify Intel Comment 7. Also a minor correction is made on one
of the drawings for consistency.

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ANY OTHER BACKGROUND INFORMATION:

This is in response to two letter ballot comments submitted in June, 1999 on
SP-4557 for EIA ratification of Version 3.2 from Cisco Systems and Intel. The
comments are shown below:

Cisco Systems Comment 1 was:

Cisco Systems: 1
Editorial
Reference: Page 24
Suggested Change: Add a hysteresis diagram showing all the sub-parameters.

Rationale: Would clarifiy usage of Vinh+, Vinh-, Vinl+, Vinl-,
S_overshoot_high, S_overshoot_low, D_overshoot_high, D_overshoot_low,
D_overshoot_time, Pulse_high, Pulse_low, Pulse_time.

Intel: 7
Editorial
Reference: Page 24
Suggested Change: the whole discussion on dynamic and static overshoot is
confusing. I can't figure out if static or dynamic overshoot implies an
absolute maximum rating or device destruction or what. Not sure how to fix,
but this does need to be clarified.

Also, another remark was dealt with by deleting one paragraph:

Intel: 6
Editorial
Reference: Page 23
Suggested Change: Delete paragraph about reversing Vinh, Vinl to mimic
hystersis. While this my be true, we have explicit parameters that
describe this functionality and we should not document or encourage an
alternate method.

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Received on Fri Aug 20 13:32:50 1999

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