Subject: TERMINATION, NEW BIRD 9

From: Will Hobbs <[email-masked]>
Date: Thu, 3 Feb 94 10:58:55 PST

Hello IBIS members:

Here is a cut at a "terminator" specification.  This one is for a minimal 
extension using the existing IBIS components plus introducing two additional 
resistors [Rpower] and [Rgnd].  It does not introduce a "terminator" Model_type.
Such an extension is an option, but it also may be related to pending BIRD2 
regarding Vinl and Vinh.

The resistor elements are desirable for efficiency.  They are technically 
available using [Power_clamp] and [Gnd_clamp] structures.  Simulators support 
resistor elements, and using them for analysis is much more efficient than using
tabular data.

Bob Ross, Interconnectix, Inc.

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Buffer Issue Resolution Document  (BIRD)

BIRD ID#:                9
ISSUE TITLE:             Terminator Specification
REQUESTOR:               Bob Ross, Interconnectix, Inc.
DATE SUBMITTED:          2 February 1994
DATE REVISED:
DATE ACCEPTED BY IBIS OPEN FORUM:     {will be filled in when accepted}

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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:

Two 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].

|=============================================================================
|    Keywords:  [Rgnd], [Rpower]
|    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) 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) 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], [POWER_clamp], [Pulldown], and
|               [Pullup] structures.
|------------------------------------------------------------------------------
|    variable        R(typ)          R(min)          R(max)
     [Rgnd]          330Ohm          300Ohm          360Ohm
     [Rpower]        220Ohm          200Ohm          NA
|==============================================================================
| The "Other Notes:" text within the [Model] Keyword description is changed
| to include references to [Rpower] and [Rgnd]:
| Other Notes:  A complete [Model] description normally contains the following
|               keywords:  [Voltage range], [Pullup], [Pulldown], [GND_clamp],
|               [POWER_clamp], [Rgnd], [Rpower],
|               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.
|               Note that C_comp defines the silicon die capacitance. This
|               value should not include the capacitance of the package.
|
|------------------------------------------------------------------------------

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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.

The following terminators do not require extensions:

(2) 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.

(3) Internal Series Resistance Terminations:

R_pkg (or R_pin) can be used to model internal series terminations.  An
alternative would be to specify an internal [Rseries] component.

(4) RC (or AC) Termination:

R_pkg (or R_pin) and C_comp can provide RC terminations.  An alternative
would be to specify [Rac] connected to [Cac] components.

Other passive networks including capacitive loads are already available
through existing package and C_comp elements.

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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 Discrete 
two-port devices except through one partial solution with internal series 
terminators.

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

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