Subject: [IBIS] BIRD80 - Add External Reference Column to Pin Mapping Keyword
From: Ross, Bob (bob_ross@mentorg.com)
Date: Mon Nov 25 2002 - 17:59:51 PST
To All:
Michael Mirmak has issued BIRD80 per the discussion at the
November 22, 2002 meeting.
Bob Ross
Mentor Graphics
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BUFFER ISSUE RESOLUTION DOCUMENT (BIRD)
BIRD ID#: 80
ISSUE TITLE: Add External Reference Column to Pin Mapping Keyword
REQUESTOR: Michael Mirmak, Intel Corporation
DATE SUBMITTED: November 25, 2002
DATE REVISED:
DATE ACCEPTED BY IBIS OPEN FORUM: Pending
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STATEMENT OF THE ISSUE:
The [Pin Mapping] keyword does not contain any means by which users can
designate [Component] pins or pads as connected to a buffer's [External
Reference] supply voltage. This BIRD expands [Pin Mapping] by adding a
sixth column for external voltage supply data, to allow [External Reference]
supplies to be mapped to particular pad or pin groups.
The changes made by this BIRD are linked to and required by the language of
BIRDs 75 and 77.
****************************************************************************
STATEMENT OF THE RESOLVED SPECIFICATIONS:
Changes are marked with the * characters.
|============================================================================
| Keyword: [Pin Mapping]
| Required: No
|* Description: Used to indicate to which power and ground buses a given
|* driver, receiver, or terminator is connected.
|* Sub-Params: pulldown_ref, pullup_ref, gnd_clamp_ref, power_clamp_ref,
|* external_ref
|* Usage Rules: Each supply voltage bus is given a unique name that must
| not exceed 15 characters. The first column contains a pin
| name. Each pin name must match one of the pin names declared
| previously in the [Pin] section of the IBIS file. The second
| column, pulldown_ref, designates the ground bus connections
|* for that pin (here the term ground bus can also mean another
|* power bus). The third column pullup_ref designates the power
| bus connection. The fourth and fifth columns gnd_clamp_ref
| and power_clamp_ref contain entries, if needed, to specify
| different ground bus and power bus connections than those
|* previously specified. Finally, the sixth column external_ref
|* contains entries to specify external reference bus
|* supply connections.
|
| If the [Pin Mapping] keyword is present, then the bus
| connections for EVERY pin listed in the [Pin] section must
| be given.
|
|* Each line must contain either three, five or six columns.
|* Use the NC reserved word for entries that are not needed or
|* that follow the conditions below:
|
| All entries with identical labels are assumed to be connected.
| Each unique entry label must connect to at least one pin whose
| model_name is POWER or GND.
|
| If a pin has no connection, then both the pulldown_ref and
| pullup_ref subparameters for it will be NC.
|
| GND and POWER pin entries and buses are designated by entries
| in either the pulldown_ref or pullup_ref columns. There is no
| implied association to any column other than through explicit
| designations in other pins.
|
| For any other type of pin, the pulldown_ref column contains
| the power connection for the [Pulldown] table for non-ECL type
| [Model]s. This is also the power connection for the [GND
| Clamp] table and the [Rgnd] model unless overridden by a
| specification in the gnd_clamp_ref column.
|
| Also, the pullup_ref column contains the power connection for
| the [Pullup] table and, for ECL type models, the [Pulldown]
| table. This is also the power connection for the [POWER
| Clamp] table and the [Rpower] model unless overridden by a
| specification in the power_clamp_ref column.
|
|* External reference voltage pins are designated in a similar
|* fashion to other POWER pins; the external reference bus name
|* should be listed under the pullup_ref column.
|*
| The column length limits are:
| [Pin Mapping] 5 characters max
| pulldown_ref 15 characters max
| pullup_ref 15 characters max
| gnd_clamp_ref 15 characters max
| power_clamp_ref 15 characters max
|* external_ref 15 characters max
|
|* For compatibility with models developed under previous IBIS
|* versions, [Pin Mapping] lines which contain external_
|* ref column entries must also explicitly include entries for
|* the pulldown_ref, pullup_ref, gnd_clamp_ref and power_clamp_
|* ref columns.
|
|* When six columns are specified, the headings gnd_clamp_ref,
|* power_clamp_ref and external_ref must be used. Otherwise,
|* these headings may be omitted.
|
|
|----------------------------------------------------------------------------
[Pin Mapping] pulldown_ref pullup_ref gnd_clamp_ref power_clamp_ref
|* This external_ref is continued on the line above external_ref
|
1 GNDBUS1 PWRBUS1 | Signal pins and their associated
* 2 GNDBUS2 PWRBUS2 | ground, power and external
|* | reference connections
3 GNDBUS1 PWRBUS1 GNDCLMP PWRCLAMP
4 GNDBUS2 PWRBUS2 GNDCLMP PWRCLAMP
* 5 GNDBUS2 PWRBUS2 NC PWRCLAMP REFBUS1
6 GNDBUS2 PWRBUS2 GNDCLMP NC
* 7 GNDBUS2 PWRBUS2 GNDCLMP NC REFBUS2
|* | Some possible clamping
|* | connections are shown above
| . | for illustration purposes
| .
11 GNDBUS1 NC | One set of ground connections.
12 GNDBUS1 NC | NC indicates no connection to
13 GNDBUS1 NC | power bus.
| .
21 GNDBUS2 NC | Second set of ground connections
22 GNDBUS2 NC
23 GNDBUS2 NC
| .
31 NC PWRBUS1 | One set of power connections.
32 NC PWRBUS1 | NC indicates no connection to
33 NC PWRBUS1 | ground bus.
| .
41 NC PWRBUS2 | Second set of power connections
42 NC PWRBUS2
43 NC PWRBUS2
| .
51 GNDCLMP NC | Additional power connections
52 NC PWRCLMP | for clamps
|
|* .
* 71 NC REFBUS1
* 72 NC REFBUS2
|
*****************************************************************************
ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:
The addition of the external reference voltage keyword, [External
Reference], effectively created a "fifth" voltage for many IBIS buffers
which previously could only use the four basic ones: [Pullup Reference],
[Pulldown Reference], [Power Clamp Reference] and [Ground Clamp Reference]
([Pullup Reference] and [Power Clamp Reference] can be addressed
simultaneously through the [Voltage Range] keyword). The IBIS 2.1 keyword
[Pin Mapping] establishes a means by which model authors can connect
"blocks" of buffer supplies to particular supply pins or pads.
Unfortunately, the [Pin Mapping] definition was limited to the four basic
supplies assumed by the [Model] keyword in IBIS 2.1. This BIRD expands [Pin
Mapping] by adding a sixth column for external voltage supply data, to allow
[External Reference] supplies to be mapped to particular pad or pin groups.
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ANY OTHER BACKGROUND INFORMATION:
Note that this BIRD assumes that IBIS has been expanded to allow more than
80 characters of data per line. At least 85 characters must be allowed in
order to accommodate four columns of 15 characters each, plus a
five-character name column and the spaces between each column.
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