IBIS Macromodel Task Group

Meeting date: 05 March 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:

- None.
  
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Review of ARs:

Michael: Review draft2 of the Block Concepts Clarification BIRD and attempt to
         streamline the language.
         - Done.  Michael reported that he had a cleaned-up version to review in
           today's meeting.
         
Arpad: Draft an editorial clarification BIRD to make it clearer to the reader
       when an AMI parameter's value in the .ami file is merely a placeholder.
       - Not Done.  Arpad said he had started to work on it, but it began to
         look more complicated than we first assumed.  See discussion below.
         Arpad said he would remove this AR.

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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 February 27th
meeting.  Ambrish moved to approve the minutes.  Michael seconded the motion.
There were no objections.

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New Discussion:

Clarification BIRD for placeholder parameter values in the .ami file:
Arpad said he had begun work on this.  However, he had run into issues that made
it appear to be more significant effort than we first assumed.  For example, in
IBIS 7.2, we find values such as "ignore_me", "0.00 0.00 0.00", "placeholder",
and other values used in placeholder situations.  Arpad said he had conferred
with Randy, who had originally raised the issue.  Randy agreed this was probably
a topic for the Editorial task group to take up later.  Randy noted that there
are already two issues in the known issues document for IBIS 7.2 related to
placeholder values.  So, the Editorial task group will eventually address this
issue.  Arpad moved to remove this item from the ATM agenda.  Ambrish seconded.
There were no objections.

AMI Block Concepts Clarification BIRD:
Michael reviewed his new cleaned-up version.  He said the changes were mostly
incorporated from Arpad's private email.  He noted one other change based on
feedback from Curtis that the definition of symbol used in draft2 was incorrect.
Curtis said that draft2 included language changes for page 216 that included
the following misleading text:
  ...NRZ (non-return-to-zero) system where only one of two logical states or
  symbols is possible in each Unit Interval...
Curtis said this mistakenly implied that symbols were the same as the logic
levels and there were two symbols per UI for NRZ.  Michael had agreed and
adopted new language.  Curtis noted, however, that he did not think this
definition of NRZ should be added in this location at all.  He said defining
every specific term in the flow of the text made it cumbersome, and it risked
alienating the reader by defining basic concepts in the middle of the AMI flow
descriptions.  Curtis said that if we felt it necessary to define everything so
precisely, then he agreed with Michael's suggestion (previous meeting) that we
should add a "Definitions" section.  This would then allow the regular text to
flow much more freely.  Curtis said he was still not entirely sure that this
clarification BIRD was necessary at all, however.

Curtis noted other language from the page 216 changes in draft2:
   ...time segments (groups of sequential waveform samples, elsewhere called
   blocks)...
He said we could streamline this language by choosing one or the other.  Why not
just use the term blocks all the time?  Arpad agreed that we should reduce the
use of synonyms in the specification.  Michael said there were subtle
differences in usage.  He said he'd drawn the equivalence in this text, but that
people often talked about time segments when thinking in terms of samples and
often used block when thinking in units of bits.  Curtis said this was one more
reason to remove the synonyms.  He said we should not use different names for
the same concept just because we are using different units.

Arpad asked why we need to explicitly emphasize "sequential" in:
  ...groups of sequential waveform samples...
Michael said the goal was to explicitly state that they would be adjacent
samples and monotonically increasing in time.  The tool would not be subsampling
or otherwise straying from the sample_interval, for example.

Michael suggested that he set this BIRD aside and start work on a different BIRD
to introduce a Definitions section.  Once that new BIRD is finished, we could
significantly streamline the language in this BIRD.  While most of the terms we
need to define initially would be from Chapter 10 (AMI), Michael suggested we
add the Definitions in Section 3, since we have many specification-wide
definitions already there.  Michael said the initial list of definitions we need
wouldn't be too long, e.g., bit, symbol, segment, block, NRZ, PAMn.

[Clock Group] Proposal:
Michael said he did not have a new update relative to last week's meeting.  He
said the goal will be to define the physical relationships between pins.  For
example, in a DDR context, which group of DQ pins utilizes a given DQS strobe.
He said defining these relationships might be complicated for a DDR controller
model, where the grouping might be configurable instead of fixed.

The timing relationships might also be important, and it might be helpful to
define them within IBIS.  One example is data sheet data such as the range of
possible deviations in timing between the data and strobe.  He said the downside
is that we have tended to avoid those types of explicit timing relationships in
IBIS.  He said it becomes difficult to accommodate corners and other variables.
Arpad noted that IBIS had generally avoided internal and even buffer timing
questions in the past.  Michael said there is always interest in delays at the
outputs.  At a minimum, however, this BIRD will seek to define which groups of
pins need to be simulated.  He said we could define the grouping relationships
now and leave the timing values to a separate future BIRD if necessary.

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

New ARs:
         
Michael: Draft a new BIRD proposal to introduce a "Definitions" section.

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

1) Simulator directives
