Subject: BIRD9.3 ("Terminator" change)

From: [email-masked] ( Bob Ross)
Date: Fri, 29 Apr 94 11:01:37 PDT

Hello IBIS members:

BIRD9.2 was approved at the April 29, 1994 meeting, but with the change
the Model_type "Discrete" be changed to "Terminator".  This is done
below, and the number is rolled to BIRD9.3

Bob Ross, Interconnectix, Inc.

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                 Buffer Issue Resolution Document  (BIRD)

BIRD ID#:                9.3
ISSUE TITLE:             Terminator Specification 
REQUESTOR:               Bob Ross, Interconnectix, Inc. 
DATE SUBMITTED:          2 February 1994
DATE REVISED:            21 February 1994, 22 April 1994, 29 April 1994
DATE ACCEPTED BY IBIS OPEN FORUM:     29 April 1994

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STATEMENT OF THE ISSUE:  

  Terminators are used in design and can exist as packaged parts.  Therefore
they are candidates for IBIS modeling.  

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STATEMENT OF THE RESOLVED SPECIFICATIONS:  

  The additional keywords, [Rpower] and [Rgnd], are proposed to represent
resistors connected to power (VCC) and ground (GND) or to the voltages based
on the voltage reference rules in BIRD3 as they apply to [POWER_clamp] and
[GND_clamp].  An AC terminator requiring both [Rac] and [Cac] to GND is
proposed.  For new keyword usage, a new Model_type parameter within
[Model] called "Terminator" is proposed.

|==============================================================================
|    Keywords:  [Rgnd], [Rpower], [Rac], [Cac]        
|    Required:  Yes, if they exist in the device                              
| Description:  The data for these keywords define the resistance values of
|               Rgnd and Rpower connected to GND and the POWER pins,           
|               respectively.                                                 
| Usage Rules:  For each of these sections the three columns hold the         
|               typical, minimum, and maximum resistance values.  The three  
|               entries for R(typ), R(min), and R(max) or C(typ), C(min),
|               and C(max) must be placed on a single line and must be    
|               separated by at least one white space or tab character.       
|               All three columns are required under these keywords, however  
|               data is only required in the typical column.  If minimum      
|               and/or maximum values are not available, the reserved word
|               "NA" must be used indicating the R(typ) or C(typ) value by
|               default.  
| Other Notes:  It should be noted that [Rpower] is connected to 'Vcc' and      
|               [Rgnd] is connected to 'GND'.  However, [GND_clamp reference] 
|               voltages, if defined, apply to [Rgnd].  [POWER_clamp reference]
|               voltages,  if defined, apply to [Rpower].                                                 |               Either or both [Rgnd] and [Rpower] may be defined and may
|               co-exist with [GND_clamp] and [POWER_clamp] structures.
|               If an AC terminator is specified, then both [Rac] and [Cac]
|               are required.
|               When [Rgnd], [Rpower], or [Rac] and [Cac] are specified, the
|               Model_type must be Terminator.
|------------------------------------------------------------------------------
| variable      R(typ)          R(min)          R(max)
|
[Rgnd]          330Ohm          300Ohm          360Ohm   | Parallel Terminator
[Rpower]        220Ohm          200Ohm          NA       |
|
[Rac]            30Ohm          NA              NA       | 
|                                                        |
| variable      C(typ)          C(min)          C(max)   | AC terminator
|                                                        |
[Cac]            50pF            NA             NA       | 
|==============================================================================

  The [Model] keyword text has "Terminator" added to the list of Model_types.
A modification to the Other Notes section refers to the the new keywords.

|==============================================================================|
|     Keyword:  [Model]                                                        |
|    Required:  Yes                                                            |
| Description:  Used to define a model, and its attributes.                    |
|  Sub-Params:  Model_type, Polarity, Enable, Vinl, Vinh, C_comp               |
|*
|* BIRD7.2 and 9.3 modifications
|* Usage Rules:  Each Input, Output, I/O, 3-state, Open_drain, I/O_open_drain,
|*               Open_sink, I/O_open_sink, Open_source, I/O_open_source,
|*               Input_ECL, Output_ECL, I/O_ECL and Terminator model must
|*
|               begin with the keyword [Model].  The model_name must match     |
|               the one that is listed under the [Pin] keyword and must not    |
|               contain more than 20 characters.  An .ibs file must contain    |
|               enough [Model] keywords to cover all of the model_names        |
|               specified under the [Pin] keyword, except for those            |
|               model_names which use reserved words (POWER, GND and NC).      |
|               Model_names with reserved words are an exception and           |
|               they do not have to have a corresponding [Model] keyword.      |
|               C_comp is allowed to use "NA" for the min and max values only. |
|*
|* BIRD9.3 change
|* Other Notes:  A complete [Model] description normally contains the following 
|*               keywords:  [Voltage range], [Pullup], [Pulldown], [GND_clamp], 
|*               [POWER_clamp], [Rgnd], [Rpower], [Rac], [Cac],
|*               and [Ramp].  However, some models may have only 
|*               a subset these keywords.  For example, an input structure      
|*               normally only needs the [Voltage range], [GND_clamp], and      
|*               possibly the [POWER_clamp] keywords.  If one or more of
|*               [Rgnd], [Rpower], [Rac] and [Cac] keywords are used, then
|*               the Model_type must be Terminator.                  
|*
|* BIRD7.2 addition
|*               Model_types with "open_sink" specify that the output has
|*               an OPEN side (the [Pullup] keyword is not used or I = 0mA
|*               for all voltages specified) AND the output SINKS current.
|*               Model_types with "open_drain" have the identical meaning and
|*               are retained for backward compatibility.  Model_types with
|*               "open_source" specify that the output has an OPEN side (the
|*               [Pulldown keyword is not used or I = 0mA for all voltages
|*               specified) AND the output SOURCES current.  Model_types with 
|*               "_ECL" specify that the model represents and ECL type logic
|*               which follows different conventions for the [Pulldown] keyword.
|*
|               Note that C_comp defines the silicon die capacitance.  This    |
|               value should not include the capacitance of the package.       |
|                                                                              |
|------------------------------------------------------------------------------|
[Model]         model_name
|*
|* BIRD7.2 and BIRD9.3 modification
Model_type      Input, Output, I/O, 3-state, Open_drain, I/O_open_drain,
                Open_sink, I/O_open_sink, Open_source, I/O_open_source,
                Input_ECL, Output_ECL, I/O_ECL, Terminator     | List one only
|*
Polarity        Non-Inverting, Inverting                | List one only, if any
Enable          Active-High, Active-Low                 | List one only, if any
| Signals       RAS, CAS, A(0-64), D(0-128),...         | Local list, if desired
Vinl = 0.8V                             | input logic "low" DC voltage, if any
Vinh = 2.0V                             | input logic "high" DC voltage, if any
| variable      typ             min             max
C_comp          12.0pF          10.0pF          15.0pF
|==============================================================================|

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:  

  A set of terminator components is useful to be formatted using IBIS because
they are found as packaged components.  All of the options can support (typ),
(min) and (max) specifications.

(1) Parallel Resistor Termination:

  The additonal elements [Rpower] and [Rgnd] provide terminations to Vcc, Gnd
or both.  Devices such as the Motorola MCC142233 to MCC142236 Switchable SCSI
Passive Bus Terminator series would be modeled with these elements. 

  At least two other techniques could be used in IBIS Version 1.1.  The 
[POWER_clamp] or [GND_clamp] tables could be used (with as few as two data
points each) to represent resistors.  Another method could be to use R_pkg
(or R_pin) with [POWER_clamp] or [GND_clamp] structures configured as a 
very low impedance.  Processing tabular data for these purposes would be less
efficient and less obvious than working with resistive elements directly.  

(2) RC (or AC) Termination:

  R_pkg (or R_pin) and C_comp can provide RC terminations.  This proposal
specifies [Rac] connected to [Cac] elements.  This will allow packaged RC
terminations which include built in clamping diodes to be modeled directly.

  Diode terminators already can be modeled using IBIS Version 1.1:

(3) Diode Termination:

  Devices such as the TI SN74S1050 thru SN74S1056 Schottky Barrier Diode
Bus-Termination Arrays can be modeled using existing [POWER_clamp] and
[GND_clamp] structures. 

  The total context model is attached showing the proposed additions. 

                        |<-------------TERMINATOR Model--------------->|

                            VOLTAGE RANGE or
                            POWER_CLAMP REF
                                   o
                                   |
                        POWER_ |---o---|
                        CLAMP  |       |
                            |--o--|    \
                            |     |    /
                            | VI  |    \ RPOWER    PACKAGE Keyword
                            |     |    /              Parameters
                            |--o--|    |        |<----------------->|
                               |       |            
                               |       |                               PIN
                         o-----o-------o-----o-----/\/\/\--UUUUUU---o--o 
                         |     |GND_   |     |      R_PKG   L_PKG   |
                         |     |CLAMP  |     |                      |
                         |  |--o--|    |     |                      |
                         |  |     |    \     |                      |
                         |  | VI  |    /RGND |                      |
                         |  |     |    \     \                      |
                         |  |--o--|    /     / RAC                  | 
                         |     |       |     \                      |
                         |     |---o---|     /                      |
                         |         |         |                      |
                 C_COMP ---        o        --- CAC          C_PKG ---
                        ---     GND or      ---                    ---
                         |   GND_CLAMP REF   |                      |
                         |                   |                      |
                         |-------------------o----------------------|
                                             |
                                             o
                                            GND

                                      |<-------->|
                                        Proposed 
                                       Terminator
                                        Keywords

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ANY OTHER BACKGROUND INFORMATION:

This BIRD partially addresses the issue related to BIRD2 regarding 
Termination Resistor Packs and Termination Diode Packs.  It does not
address Terminator two-port devices.

The adoption of this BIRD would require some text changes in BIRD3 to 
reference the new keywords.

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