New bird flying by, see if you can catch it...

Text item: Text_1

               Buffer Issue Resolution Document (BIRD)

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

DATE SUBMITTED: April 26, 1994
DATE ACCEPTED BY IBIS OPEN FORUM:

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

STATEMENT OF THE ISSUE:

       It is desirable to have two 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.
       Two new sub-parameters, Cref (a reference specload) and Vt (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, Vt, 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, six for Vinl, six for Vinh, five for Vt,
| 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 fifty-two
| characters.
|
|*************************************************************************

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

[SPECS]
| C_comp
Pin Vinl Vinh Vt Cref typ min max
1 0.8V 2.0V 1.5V 50pF 4.5pF 3.0pF 6.0pF
4 NA NA 2.5V 30pF NA NA NA
9 1.5V 3.5V NA 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: ..., Vt, Cref
|
| Other Notes: ... Component timings are usually specified into a
| reference capacitance that can be listed as Cref. Vt 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
Vt=1.5V |Test voltage timings are specified to
Cref=50pF |Reference capacitance timings are specified into

The Cref and Vt 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 Cref and Vt and all other sub-parameters of a
[Model] are to be used as default values only. All sub-parameters in
a [Model] are overriden by any values listed in the [SPECS] section.

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

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

ANY OTHER BACKGROUND INFORMATION:

*************************************************************************
Received on Wed Apr 27 12:41:50 1994