Subject: [IBIS] BIRD80.1 - Add External Reference Column to Pin Mapping Keyword
From: Peters, Stephen (stephen.peters@intel.com)
Date: Mon Jan 06 2003 - 13:59:49 PST
Greetings:
Per the last IBIS teleconference, Michael Mirmak has updated BIRD80. We
will be discussing the changes at the January 10, 2002 IBIS teleconfence.
Regards,
Stephen Peters
Intel Corp.
Chair, EIA/IBIS Open Forum
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BUFFER ISSUE RESOLUTION DOCUMENT (BIRD)
BIRD ID#: 80.1
ISSUE TITLE: Add External Reference Column to Pin Mapping Keyword
REQUESTOR: Michael Mirmak, Intel Corporation
DATE SUBMITTED: November 25, 2002
DATE REVISED: January 6, 2003
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.
****************************************************************************
STATEMENT OF THE RESOLVED SPECIFICATIONS:
Changes to the IBIS 4.0 text are marked with the * character.
Changes from BIRD 80 to BIRD 80.1 are marked with the ** characters.
|===========================================================================
=
| Keyword: [Pin Mapping]
| Required: No
|** Description: Used to indicate the power and/or ground buses to which a
|** given driver, receiver or terminator is connected.
|* Sub-Params: pulldown_ref, pullup_ref, gnd_clamp_ref, power_clamp_ref,
|** ext_ref
|** Usage Rules: The [Pin Mapping] keyword names the connections between
|** POWER and/or GND pins and buffer and/or terminator voltage
|** supply references using unique bus labels. All buses with
|** identical labels are assumed to be connected with an ideal
|** short. Each label must be associated with at least one pin
|** whose model_name is POWER or GND. Bus labels must not
|** exceed 15 characters.
|
| Each line must contain either three, five or six entries.
|** Use the reserved word NC where an entry is required but a
|** bus connection is not made (see below).
|
| The first column contains a pin name. Each pin name must
| match one of the pin names declared in the [Pin] section of
|** the [Component].
|
|** For buffers and terminators, the remaining columns
|** correspond to the voltage supply references for the named
|** pin. Each [Model] supply reference is connected to a
|** particular bus through a bus label in the corresponding
| column.
|
| The second column, pulldown_ref, designates the ground
| bus connections for the buffer or termination associated
|** with that pin. The bus named under pulldown_ref is
|** associated with the [Pulldown] I-V table for non-ECL
|** [Model]s. This is also the bus associated with the
|** [GND Clamp] I-V table and the [Rgnd] model unless
|** overridden by a label in the gnd_clamp_ref column.
|
| The third column, pullup_ref, designates the power bus
|** connection for the buffer or termination. The bus named
| under pullup_ref is associated with the [Pullup] table for
|** non-ECL [Model]s (for ECL models, this bus is associated
|** with the [Pulldown] table). This is also the bus label
|** associated with the [POWER Clamp] I-V table and the
|** [Rpower] model unless overridden by a label in the
|** power_clamp_ref column.
|
| The fourth and fifth columns, gnd_clamp_ref and
| power_clamp_ref, contain entries, if needed, to specify
| additional ground bus and power bus connections for clamps.
|** Finally, the sixth column, ext_ref, contains entries to
|** specify external reference supply bus connections.
|
|** The usage of the columns changes for GND and POWER pins.
|** For GND pins, the pulldown_ref column contains the name of
|** the bus to which the pin connects; the pullup_ref
|** column in this case must contain the reserved word NC.
|** Similarly, for POWER (including external reference) pins,
|** the pullup_ref column contains the name of the bus to
|** which the pin connects; the pulldown_ref column in this
|** case must contain the reserved word NC.
|
|
| If the [Pin Mapping] keyword is present, then the bus
| connections for EVERY pin listed under the [Pin] keyword
| must be given.
|
| If a pin has no connection, then both the pulldown_ref and
| pullup_ref subparameters for it will be NC.
|
| 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
|** ext_ref 15 characters max
|
|* For compatibility with models developed under previous IBIS
|** versions, [Pin Mapping] lines which contain ext_ref column
|* entries must also explicitly include entries for the
|* pulldown_ref, pullup_ref, gnd_clamp_ref and power_clamp_ref
|** columns. These entries can be NC, as explained above.
|
|** When six columns of data are specified, the headings
|** gnd_clamp_ref, power_clamp_ref and ext_ref must be used on
|** the line containing the [Pin Mapping] keyword. Otherwise,
|** these headings can be omitted.
|
|---------------------------------------------------------------------------
-
**[Pin Mapping] pulldown_ref pullup_ref gnd_clamp_ref power_clamp_ref
ext_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 | External reference connections
** 72 NC REFBUS2
|
|** The following [Pin] list corresponds to the [Pin Mapping] shown above.
|**
** [Pin] signal_name model_name R_pin L_pin C_pin
| **
** 1 OUT1 output_buffer1 | Output buffers
** 2 OUT2 output_buffer2 |
** 3 IO3 io_buffer1 | Input/output buffers
** 4 IO4 io_buffer2 |
** 5 SPECIAL1 ref_buffer1 | Buffers with POWER CLAMP but no
** 6 SPECIAL2 io_buffer_term1 | GND CLAMP I-V tables; two use
** 7 SPECIAL3 ref_buffer2 | external reference voltages
** 11 VSS1 GND
** 12 VSS1 GND
** 13 VSS1 GND
** 21 VSS2 GND
** 22 VSS2 GND
** 23 VSS2 GND
** 31 VCC1 POWER
** 32 VCC1 POWER
** 33 VCC1 POWER
** 41 VCC2 POWER
** 42 VCC2 POWER
** 43 VCC2 POWER
** 51 VSSCLAMP GND | Power connections for clamps
** 52 VCCCLAMP POWER |
** 71 V_EXTREF1 POWER | External reference voltage pins
** 72 V_EXTREF2 POWER |
|
****************************************************************************
*
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
buffer or terminator supply references to particular POWER and GND pins.
However, the [Pin Mapping] definition was limited to the four basic
supplies assumed by the [Model] keyword in IBIS 2.1. BIRD 80 expands [Pin
Mapping] by adding a sixth column for external voltage supply reference
labels, to allow [External Reference] supplies to be mapped to particular
pins.
BIRD 80.1 is issued in response to comments by Frank Dunlap, Arpad Muranyi
and Bob Ross. Accordingly, the "external_reference" column is changed to
"ext_ref" to be compliant with the current 80 column IBIS line-length
requirement. Several other changes have been made in BIRD 80.1, as
explained below.
In IBIS 4.0 and previous versions, the "pulldown_ref" and "pullup_ref"
columns served two functions. For signal pins, these columns contained
the labels of the bus connections for the pulldown and pullup supplies,
respectively. Additionally, these columns were used to declare to which
buses POWER and GND pins were connected. Even if a buffer used a particular
bus and its associated POWER pin only for its [POWER Clamp] I-V tables,
the bus name for that POWER pin was required to be listed under the
pullup_ref column, with an NC listed under the pulldown_ref column.
BIRD 80.1 maintains this approach, for consistency. Therefore, ext_ref
supply pins can only be declared under the pulldown_ref or pullup_ref
columns and in no other column. The IBIS parser should check the placement
of ext_ref bus labels as appropriate.
In addition, the word "previously" in reference to the [Pin] section of an
IBIS model has been removed in BIRD 80.1. There are no explicit rules in
the IBIS specification which require that the [Pin] keyword must appear
before the [Pin Mapping] keyword.
Other grammatical and clarity issues, some found in versions as early as
IBIS 2.1, have been corrected in BIRD 80.1, with no impact to the
usage model of the keyword.
****************************************************************************
*
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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