Subject: [IBIS] BIRD87 - Series Pin Mapping Clarifications
From: Mirmak, Michael (michael.mirmak@intel.com)
Date: Mon Jan 19 2004 - 08:37:05 PST
The enclosed document, BIRD87, is posted on behalf of Arpad Muranyi of
Intel Corporation. It will be introduced at the January 30, 2004 IBIS
Open Forum teleconference.
- Michael Mirmak
Intel Corp.
Chair, EIA/IBIS Open Forum
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BUFFER ISSUE RESOLUTION DOCUMENT (BIRD)
BIRD ID#: BIRD87
ISSUE TITLE: Series Pin Mapping Clarifications
REQUESTOR: Arpad Muranyi, Intel Corporation
DATE SUBMITTED: January 19, 2004
DATE REVISED:
DATE ACCEPTED BY IBIS OPEN FORUM: Pending
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STATEMENT OF THE ISSUE:
The usage rules of the [Series Pin Mapping] keyword in the IBIS 4.0/4.1
specification fails to mention that the third column (model_name) may
also
reference a [Model Selector] name, not just [Model] name.
Also, the usage rules section does not mention whether using the same
pin
name in multiple associations with models or model selectors is
prohibited
or not. Strictly speaking, the absent prohibition implies that it is
allowed,
but spelling out this rule could eliminate questions and confusion.
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STATEMENT OF THE RESOLVED SPECIFICATIONS:
Add a few more words to the usage rules as shown below to clarify the
issues
mentioned above. Changes are marked with the * characters at the
beginning
of each line.
|=======================================================================
====
| Keyword: [Series Pin Mapping]
| Required: No
| Description: Used to associate two pins joined by a series model.
| Sub-Params: pin_2, model_name, function_table_group
| Usage Rules: Enter only series pin pairs. The first column, [Series
Pin
| Mapping], contains the series pin for which input
impedances
| are measured. The second column, pin_2, contains the
other
| connection of the series model. Each pin must match the
pin
| names declared previously in the [Pin] section of the
IBIS
|* file. The third column, model_name, associates models
of
|* type Series or Series_switch, or model selectors
containing
|* references to models of type Series or Series_switch for
|* the pair of pins in the first two columns. Each
model_name
|* must have a corresponding model or model selector name
|* listed in a [Model] or [Model Selector] keyword below.
The
|* usage of reserved model names (POWER, GND, or NC) within
the
|* [Series Pin Mapping] keyword is not allowed. The fourth
| column, function_table_group, contains an alphanumeric
| designator string to associate those sets of
Series_switch
| pins that are switched together.
|
| Each line must contain either three or four columns.
When
| using four columns, the header function_table_group must
be
| listed.
|
| One possible application is to model crossbar switches
where
| the straight through On paths are indicated by one
| designator and the cross over On paths are indicated by
| another designator. If the model referenced is a Series
| model, then the function_table_group entry is omitted.
|
| The column length limits are:
| [Series Pin Mapping] 5 characters max
| pin_2 5 characters max
| model_name 20 characters max
| function_table_group 20 characters max
|
| Other Notes: If the model_name is for a non-symmetrical series model,
| then the order of the pins is important. The [Series
Pin
| Mapping] and pin_2 entries must be in the columns that
| correspond with Pin 1 and Pin 2 of the referenced model.
|
| This mapping covers only the series paths between pins.
The
| package parasitics and any other elements such as
additional
| capacitance or clamping circuitry are defined by the
| model_name that is referenced in the [Pin] keyword. The
| model_names under the [Pin] keyword that are also
referenced
| by the [Series Pin Mapping] keyword may include any
legal
| model or reserved model except for Series and
Series_switch
| models. Normally the pins will reference a [Model]
whose
| Model_type is 'Terminator'. For example, a
Series_switch
| model may contain Terminator models on EACH of the pins
to
| describe both the capacitance on each pin and some
clamping
| circuitry that may exist on each pin. In a similar
manner,
| Input, I/O or Output models may exist on each pin of a
| Series model that is serving as a differential
termination.
|
|* Also, a pin name may appear on more than one entry under
the
|* [Series Pin Mapping] keyword. This allows for multiple
and
|* perhaps different models or model selectors to be placed
|* between the same, or any arbitrary pin pair
combinations.
|-----------------------------------------------------------------------
---- ************************************************************************ ****ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:
Since the usage rules of the [Pin] keyword includes this statement:
| ... 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).
and the usage rules of the [Model Selector] keyword includes this statement:
| ... The name of the | [Model Selector] keyword must match the corresponding model | name listed under the [Pin] or [Series Pin Mapping] keyword | and must not contain more than 20 characters.
the intent was obviously to allow the [Series Pin Mapping] keyword to reference [Model Selectors]. The missing statement under the [Series Pin Mapping] keyword seems to have been just and editorial oversight.
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ANY OTHER BACKGROUND INFORMATION:
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