Subject: BIRD 14.1

From: Derrick Duehren <[email-masked]>
Date: Thu, 19 May 94 20:40:01 PST

Text item: Text Item

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

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            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:                       April 26, 1994
DATE REVISED:                         May 18, 1994 
DATE ACCEPTED BY IBIS OPEN FORUM:     Pending

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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.

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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.

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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.

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ANY OTHER BACKGROUND INFORMATION:

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