Subject: BIRD 14.1, Updated from John Keifer

From: Don A Telian <[email-masked]>
Date: Thu, 19 May 94 10:00:03 PST

Text item: Text_1

To: IBIS Committee

Here is the updated BIRD14 with the suggested fixes.  This includes
Model_type, Rref, and Vref being added to the [SPECS] section, Rref
and Vref being optionally added to all model files, and Vt being changed
to Vtest to be clearer on the meaning.  I have asked around and to my
knowledge everyone agrees with these changes and with this updated BIRD.
If anyone has any further problems with this BIRD, please put them on the
reflector and let me know.

Note:  No defaults were added for backcompatability.  This means that with
this BIRD, if an old IBIS Model is used that doesn't have the parameters
of this BIRD, the parameter is ignored (i.e. there is no official default
configuration for the simulator, and the Model is treated just like it is
presently with IBIS Version 1.1).  The user has the choice to either use
an old Model as it is, obtain a new Model from their vendor, or obtain the
needed data book and edit(upgrade) the Model themselves.

John Keifer

*************************************************************************

Buffer Issue Resolution Document  (BIRD)

BIRD ID#: 14.1
ISSUE TITLE:   Adding a new section for [Model] sub-parameters
REQUESTER:     John Keifer at Intel

DATE SUBMITTED:                       May 18, 1994
DATE ACCEPTED BY IBIS OPEN FORUM:

************************************************************************* 
*************************************************************************

STATEMENT OF THE ISSUE:

It is desirable to have four new sub-parameters added to a [Model] in
order to fully represent the characteristics of a given component's I/O
cells. These sub-parameters are desirable for the user of the IBIS
[Models] who wishes to perform board level simulations.  It is also
desirable to have a new optional keyword added to the top of an .IBS file
in order to parameterize the sub-parameters of a [Model] so that each
time a [Model] is used with a different sub-parameter a new [Model] would
not have to be made.

*************************************************************************

STATEMENT OF THE RESOLVED SPECIFICATIONS:

A new keyword, [SPECS], is added to the .IBS file.  The keyword [SPECS] and
all of its sub-parameters are optional.  The sub-parameters under this
keyword override the sub-parameters of a [Model].  Only those pins should be 
listed in the [SPECS] section which need to override the default
sub-parameters of a [Model].  All sub-parameters must be filled in on a line 
either with NA or a value.
Four new sub-parameters, Cref (a reference specload), Rref (a reference 
resistance), Vref (a reference voltage), and Vtest (a test voltage), are
added to a [Model].  These sub-parameters are also optional.

|*************************************************************************
|
|    Keyword:    [SPECS]
|   Required:    No
|Description:    Used to list pin-level specifications that differ from
|                the more global sub-params listed under [Model] below.
| Sub-Params:    Vinl, Vinh, Vtest, Rref, Vref, Cref, C_comp
|Usage Rules:    Only pins that have values different from the default
|                values specified in [Model] sub-parameters should be
|                listed.  Sub-parameters not used on a line must be
|                filled in with NA.
|                The [SPECS] section consists of five characters for a
|                pin number, ten for Model_type, six for Vinl, six for
|                Vinh, five for Vtest, five for Rref, five for Vref, five
|                for Cref, and six for each of the three sub-parameters
|                in C_comp.  These three sub-parameters represent the
|                following:  typ, min, and max.  All sub-parameters must
|                be separated by at least one blank space.  This comes
|                to a total of seventy-five characters.
|
|*************************************************************************

Example:  Pin1 = I/O, Pin4 = Output/3-state, Pin9 = Input

[SPECS]
|                                                      C_comp
Pin   Model_type Vinl   Vinh   Vtest Rref  Vref  Cref  typ    min    max
1     NA         0.8V   2.0V   1.5V  NA    NA    50pF  4.5pF  3.0pF  6.0pF
4     NA         NA     NA     2.5V  NA    NA    30pF  NA     NA     NA
9     NA         1.5V   3.5V   NA    NA    NA    NA    NA     NA     NA
12    I/O        NA     NA     NA    NA    NA    NA    NA     NA     NA
13    NA         NA     NA     NA    50    5V    NA    NA     NA     NA

This section will be placed directly underneath the pin list (the [Pin]
keyword section).

The [Model] section should be changed as shown below, only changes are listed.
|*************************************************************************
|
|      Keyword: [Model]
|         .
|         .
|   Sub-Params:   ..., Vtest, Rref, Vref, Cref
|
|  Other Notes:   ...   Component timings are usually specified into a 
|               reference capacitance that can be listed as Cref, or into
|               a reference resistance, Rref, pulled to a reference voltage,
|               Vref.  Vtest is the test voltage at a driver that timings are
|               specified to.  (This is usually around the 50% level of the
|               voltage thresholds.  For example, TTL=1.5V, CMOS=2.5V.)
|
|*************************************************************************

Example:

[Model]         IB080812
Model_type      I/O
Polarity        Non-Inverting
Enable          Active-High
| Signals       A[2-17]
Vinl = 0.8V
Vinh = 2.0V
Vtest=1.5V            |Test voltage timings are specified to
Rref=NA               |Reference resistance
Vref=NA               |Reference voltage
Cref=50pF             |Reference capacitance timings are specified into

The Vtest, Rref, Vref, and Cref sub-parameters would be placed inside each
[Model] file, after Vinh.

*************************************************************************

ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

Presently if a particular [Model] needs to be used for a couple 
of buffers in which the only differences are in the Vinl, Vinh, or C_comp 
sub-parameters, separate [Model]s have to be made.  With the [SPECS]
keyword, only one [Model] has to be made with the sub-parameters being
passed down from the [SPECS] section.  This feature will reduce the size
of the .IBS file.  The [SPECS] section allows separating the details from
the core of a [Model], and at the same time, gives the user the
sub-parameters he needs.  The [SPECS] keyword is also optional and hence
fully backward compatible.

The keywords Vtest, Rref, Vref, and Cref and all other sub-parameters
of a [Model] are to be used as default values only.  All sub-parameters in
a [Model] are overridden by any values listed in the [SPECS] section.

All of the data in the [SPECS] section, Vtest, Rref, Vref, and Cref is
standard data available in data books.  Allowing the specification of
Vtest, Rref, Vref, and Cref enhances the usability of an IBIS model by
providing key parameters for simulation.

*************************************************************************

ANY OTHER BACKGROUND INFORMATION:

*************************************************************************