IBIS Macromodel Task Group

Meeting date: 09 April 2024

Members (asterisk for those attending):
Achronix Semiconductor:       Hansel Dsilva
Amazon:                       John Yan
ANSYS:                      * Curtis Clark
                              Wei-hsing Huang
Aurora System:                Dian Yang
                              Raj Raghuram
Cadence Design Systems:     * Ambrish Varma
                              Jared James
Dassault Systemes:            Longfei Bai                             
Google:                       Hanfeng Wang
                              GaWon Kim
Intel:                      * Michael Mirmak
                              Kinger Cai
                              Chi-te Chen
                              Liwei Zhao
                              Alaeddin Aydiner
Keysight Technologies:        Fangyi Rao
                              Majid Ahadi Dolatsara
                              Stephen Slater
                              Ming Yan
                              Rui Yang
Marvell:                      Steve Parker
Mathworks (SiSoft):           Walter Katz
                              Graham Kus
Micron Technology:            Justin Butterfield
Missouri S&T:                 Chulsoon Hwang
                              Yifan Ding
                              Zhiping Yang
Rivos:                        Yansheng Wang
SAE ITC:                      Michael McNair
Siemens EDA (Mentor):       * Arpad Muranyi
                            * Randy Wolff
Teraspeed Labs:               [Bob Ross]
Zuken USA:                    Lance Wang

The meeting was led by Arpad Muranyi.  Curtis Clark took the minutes.

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Opens:

- Arpad noted that the meeting scheduled for April 2nd had been cancelled
  because of limited attendee availability.
  
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Review of ARs:
         
Michael: Submit draft4 of the Block Clarification proposal to IBIS Open Forum.
         - Done.  It was submitted as BIRD231.

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Call for patent disclosure:

- None.

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Review of Meeting Minutes:

Arpad asked for any comments or corrections to the minutes of the March 26th
meeting.  Michael moved to approve the minutes.  Ambrish seconded the motion.
There were no objections.

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New Discussion:

Fixing [Clock Pins]:
Michael briefly reviewed the topic and summarized discussions from previous
meetings.  He said BIRD208 had introduced [Clock Pins] into IBIS 7.1 back in
2021.  He said the goal of [Clock Pins] had been to associate clock pins with
their clocked (e.g., data) pins.  It could establish the association, but it did
not define the exact relationship.  He said [Clock Pins] works well for DRAMs,
but it was discovered that it does not easily support DDR controllers.  A
controller might have multiple modes.  It might be configurable to support 4
data lines (nibble) or 8 data lines (byte) from a given clock line, for example.
[Clock Pins] does not easily support such a configurable device, as the pin
associations are defined once when the .ibs file is created.  It does not easily
support switching between two different sets of associations, i.e., two
different modes.  Michael said that we need something analogous to a
[Model Selector] to support configurable devices such as DDR controllers.

Michael proposed a new solution that would repurposes the third column (the
relationship sub-param) in the [Clock Pins] keyword.  The third column could
contain a value indicating a grouping, which could serve as a clock selector.
Michael reviewed a [Clock Pins] example illustrating the nibble and byte cases
in the same [Clock Pins] keyword using different "x4" and "x8" groupings.

[Clock Pins] clocked_pins relationship 
A1            B1           x4 | Pins B1, B2, B3, B4 use clock information from A1
A1            B2           x4 | and can be organized as x4
A1            B3           x4 
A1            B4           x4 
A2            B5           x4 | Pins B5, B6, B7, B8 use clock information from A2
A2            B6           x4 | and can be organized as x4
A2            B7           x4 
A2            B8           x4
| 
A1            B1           x8 | Pins B1, B2, B3, B4 
A1            B2           x8 | B5, B6, B7, B8 use clock information from A1
A1            B3           x8 | and can be organized as x8
A1            B4           x8 
A1            B5           x8 
A1            B6           x8 
A1            B7           x8 
A1            B8           x8

Michael said the changes required would be to lift the current (7.2) restriction
that says only "Unspecified" is allowed in the relationship column, and remove
the following sentence:
   The structure of [Clock Pins] assumes that the clocking relationships cannot
   be redefined dynamically for the given [Component] (for example, the number
   of data pins supported by any one clock pin is fixed).
   
Arpad said we have to be careful about the term "dynamically".  He asked whether
we explicitly state that you can't change the selection during simulation.  He
said that for [Model Selector] we don't seem to explicitly state that it can't
be changed during the simulation, but it is strongly implied by this sentence
from the Usage Rules:
   The purpose of the descriptions is to aid the user of the EDA tool in making
   intelligent buffer mode selections and it can be used by the EDA tool in a
   user interface dialog box as the basis of an interactive buffer selection
   mechanism.
   
Michael agreed that the issue is the meaning of "dynamic".  He said that in this
[Clock Pins] language he thought of static as meaning that the pin associations
were defined at the time of model creation and can't be changed.  By "dynamic"
he meant that we would be able to handle a mode of operation change, which might
occur with a reboot or configuration change or firmware change.  The clock
selector concept would allow us to do this.  Michael said the intent was never
to support changing pin relationships in the middle of a simulation.

Michael noted that he would be unable to attend the next two meetings.  Given
that the agenda was sparse aside from Michael's proposals, the group decided to
cancel the meetings scheduled for April 16th and April 23rd.

- Michael: Motion to adjourn.
- Curtis: Second.
- Arpad: Thank you all for joining.

New ARs:
         
None.

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Next meeting: 30 April 2024 12:00pm PT
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IBIS Interconnect SPICE Wish List:

1) Simulator directives
