Subject: [IBIS] BIRD81 - Clarify Usage Rule for [Pin] I/O Model Assignment
From: Ross, Bob (bob_ross@mentorg.com)
Date: Mon Dec 23 2002 - 13:10:36 PST
To IBIS Committee:
BIRD81 by Lance Wang is issued to clarify some text in IBIS Version 4.0.
Bob Ross
Mentor Graphics
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Buffer Issue Resolution Document (BIRD)
BIRD ID#: 81
ISSUE TITLE: Clarify Usage Rule for [Pin] I/O Model Assignment
REQUESTOR: Lance Wang, Cadence Design Systems, Inc.
DATE SUBMITTED: 12/23/2002
DATE ACCEPTED BY IBIS OPEN FORUM: Pending
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STATEMENT OF THE ISSUE:
IBIS model makers/users often mistakenly assign a Series/Series_switch
model to pins in [Pin] section. Series/Series_switch type model or a
[Model Selector] which contains Series/Series_switch models should not
be assigned directly to a single pin by its definition. It should be only
assigned in [Series Pin Mapping] for a pin pair.
A little description in [Series Pin Mapping] Notes is not enough to drive
he better quality IBIS models.
Clarification is necessary in the usage rules of [Pin] section.
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STATEMENT OF THE RESOLVED SPECIFICATIONS:
The [Pin] keyword from the Draft Version 4.0 document is modified to
clarify the usage rules for Series/Series_switch type model.
Changes are shown by |* lines.
|=============================================================================
| Keyword: [Pin]
| Required: Yes
| Description: Associates the component's I/O models to its various external
| pin names and signal names.
| Sub-Params: signal_name, model_name, R_pin, L_pin, C_pin
| Usage Rules: All pins on a component must be specified. The first column
| must contain the pin name. The second column, signal_name,
| gives the data book name for the signal on that pin. The
| third column, model_name, maps a pin to a specific I/O buffer
| model or model selector name. Each model_name must have a
| corresponding model or model selector name listed in a [Model]
| or [Model Selector] keyword below, unless it is a reserved
| model name (POWER, GND, or NC).
|
|* Series and Series_switch type models can not be used in this
|* section directly by its definition. [Model Selector] that
|* contains series or/and Series_switch type models can not be
|* used here for the same reasons.
|*
| Each line must contain either three or six columns. A pin
| line with three columns only associates the pin's signal and
| model. Six columns can be used to override the default
| package values (specified under [Package]) FOR THAT PIN ONLY.
| When using six columns, the headers R_pin, L_pin, and C_pin
| must be listed. If "NA" is in columns 4 through 6, the
| default packaging values must be used. The headers R_pin,
| L_pin, and C_pin may be listed in any order.
|
| Column length limits are:
| [Pin] 5 characters max
| model_name 20 characters max
| signal_name 20 characters max
| R_pin 9 characters max
| L_pin 9 characters max
| C_pin 9 characters max
|-----------------------------------------------------------------------------
[Pin] signal_name model_name R_pin L_pin C_pin
|
1 RAS0# Buffer1 200.0m 5.0nH 2.0pF
2 RAS1# Buffer2 209.0m NA 2.5pF
3 EN1# Input1 NA 6.3nH NA
4 A0 3-state
5 D0 I/O1
6 RD# Input2 310.0m 3.0nH 2.0pF
7 WR# Input2
8 A1 I/O2
9 D1 I/O2
10 GND GND 297.0m 6.7nH 3.4pF
11 RDY# Input2
12 GND GND 270.0m 5.3nH 4.0pF
| .
| .
| .
18 Vcc3 POWER
19 NC NC
20 Vcc5 POWER 226.0m NA 1.0pF
|
|*21 BAD1 Series_switch1 Illegal assignment
|*22 BAD2 Series_selector1 Illegal assignment
|=============================================================================
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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:
Series and Series_switch models are designed for a pair of pins. When assign
Series/Series_switch model to a single pin, the EDA tools can not correctly
build the connections with pins and Series/Series_switch models. We
found many cases of bad IBIS models due to this issue. They were made by
IC vendors, SI Engineers and even model vendors/experts.
IBIS golden parser does not report this error either. BUG77 reports this
ibischk3 bug.
Clarification is necessary for the documentation.
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ANY OTHER BACKGROUND INFORMATION:
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