IBIS Macromodel Task Group

Meeting date:22 June 2021

Members (asterisk for those attending):
Achronix Semiconductor:       Hansel Dsilva
Amazon:                     * John Yan
ANSYS:                      * Curtis Clark
                            * Wei-hsing Huang
Cadence Design Systems:     * Ambrish Varma
                              Ken Willis
                              Jared James
Google:                       Zhiping Yang
Intel:                        Michael Mirmak
                              Kinger Cai
                              Alaeddin Aydiner
Keysight Technologies:      * Fangyi Rao
                            * Radek Biernacki
                              Ming Yan
                              Todd Bermensolo
                            * Rui Yang
Luminous Computing            David Banas
Marvell                       Steve Parker
Micron Technology:          * Randy Wolff
                            * Justin Butterfield
Missouri S&T                  Chulsoon Hwang
Siemens EDA (Mentor):       * Arpad Muranyi
SiSoft (Mathworks):         * Walter Katz
                              Mike LaBonte
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:
  
- Bob noted that the parser developer for ibischk7.1 had asked some questions
  about checking for the existence of AMI_Impulse in the executable model
  depending on the values of BCI_Training_Mode (BIRD201.1).  Arpad suggested we
  could talk about this at the beginning of the meeting, as it potentially
  affects the delivery of an IBIS7.1 parser.

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Review of ARs:

- None.

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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 June 15th
meeting.  Ambrish moved to approve the minutes.  Randy seconded the motion.
There were no objections.

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New Discussion:

AMI_Impulse existence check question:
Bob relayed a question from the parser developer working on ibischk7.1.  If
BCI_Training_Mode has allowed values of "Impulse" or "Both", then the new
AMI_Impulse function must also exist?  The group agreed it should and that
ibischk should check for the existence of AMI_Impulse under those conditions.

Another question was whether Init_Returns_Impulse should be True under the
same conditions.  Randy noted that it's clear from BIRD201.1 that AMI_Impulse
will modify the IR as part of its training.  Is there a case where AMI_Init
would not modify the response (Init_Returns_Impulse set to False) and
AMI_Impulse exists?  Ambrish said you would assume AMI_Init would also modify
the IR if AMI_Impulse exists, for example, in case there's an EDA tool that
doesn't support the BCI statistical training.  Radek noted that the BIRD
currently doesn't say anything about Init_Returns_Impulse.  He suggested a
simple solution would be to state that if you have BCI training parameters
for statistical mode training, but Init_Returns_Impulse is set to False, then
training will not proceed.

Walter said you could conceivably have an Rx doing training that does not return
an impulse from its AMI_Init because the Rx is training the Tx.  He said a Tx
doing BCI statistical training would have to return a modified IR from its
AMI_Init, or it wouldn't make sense.  Ambrish suggested that for simplicity we
should just require that Init_Returns_Impulse be True for the Tx and the Rx if
BCI statistical training is advertised/allowed.  Walter said he had no objection
to requiring it for both the Tx and Rx.  Bob also said he had no objections.

Randy asked if this would be an update to the Usage Rules for BCI_Training_Mode.
Arpad agreed it would, but he said it's a technical change and asked if it could
be handled in Editorial.  The group decided it would be best to consider a BIRD
for this change.  Bob to work out the details with the Quality task group [AR].

Radek asked whether IBIS 7.0 explicitly states that Get_Wave_Exists must be True
for time domain BCI training.  Ambrish confirmed that it does (in the Usage
Rules: for BCI_Protocol).

BIRD211.3 draft:
Fangyi reviewed and shared the new post-BIRD211.2 draft he had emailed to ATM
the day before the meeting.  He had captured all the changes from the previous
meeting's discussions of Ambrish's comments.  From Fangyi's email's summary of
the changes:

1. Clarified that for a terminal Tx the upstream impulse response is a unit
   impulse response
2. Clarified that if the EDA tool adds a unit impulse response to aggressor
   columns then it shall also increase the value of argument aggressor by one
3. Clarified that "Tx filter impulse response" is "determined" by the EDA tool
4. Separated statistical and time domain flows and removed mention of
   "initialization flow"
5. Consolidated repeated notes about old flow in Redriver flow section.
6. For symmetry, added this sentence:
   "By setting Tx_Impulse_Input to "Downstream", the model maker is declaring
    that the Tx initialization (AMI_Init) function does not have the ability
    to adapt itself based on the upstream channel."
     
The group then discussed additional suggestions from Ambrish.

1. Ambrish asked if "unit impulse response" was now being used in the text
   before it was defined.
2. Ambrish noted that consistency between existing and new figures could be
   improved.  He said the Tx and Rx devices were shown as polygons in legacy
   figures but as rectangles in some of the new figures.  Arpad said the
   polygons were used in top level physical channel figures, but he agreed that
   we should be consistent.  Ambrish said he actually preferred the polygons.
   Fangyi agreed the Tx and Rx in physical channel figures should be shown as
   polygons.
3. Ambrish asked if the "Latch" location shown in some new figures was
   necessary.  Fangyi said he thought "Latch" should remain in the flow diagrams
   but not be shown in the physical channel diagrams.
4. Ambrish suggested that including the figure for the existing Redriver
   statistical flow, which is being replaced anyway, will just cause confusion.
   He said that illustrating it, only to then say it is being replaced, is not
   necessary.  Arpad agreed and said that this section had caused confusion
   when he first read it.  They also questioned the text and the "pre 7.2"
   AMI_Version discussion.  Arpad said the concept was clear but the language
   was labored.  Ambrish suggested we simply remove the legacy diagram and the
   "pre 7.2" related sentences.  Curtis said that we could avoid the use of the
   version specific text, because "If Tx_Impulse_Input is not present"
   implicitly covers all models prior to the version in which Tx_Impulse_Input
   is introduced.  Fangyi agreed that we could work on streamlining this
   section.
5. In the Definition of the Issue section of the BIRD, Ambrish noted that the
   third item in the list of known issues in the Redriver statistical flow is
   not restricted to that flow alone.  The group added text to the third item
   stating that it also can affect the regular single channel flow.
6. Bob suggested that we have so many names, e.g., AMI functions, arguments,
   Reserved Parameters, that it might be helpful in some places to explicitly
   state "Reserved Parameter" before using a parameter name, etc.  Fangyi said
   he thought some of these suggestions could be handled in Editorial.  Bob
   and Arpad mentioned that this BIRD would now be relative to IBIS 7.1, not
   IBIS 7.0, so some references would have to change.

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

AR: Bob to work with the Quality task group on a BIRD to address the AMI_Impulse
    existence requirement and the Init_Returns_Impulse set to True requirement
    for statistical BCI mode.
AR: Fangyi to create a new draft of BIRD211.3 with the changes discussed in
    today's meeting and some additional comments from Arpad via email.

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Next meeting: 29 June 2021 12:00pm PT
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IBIS Interconnect SPICE Wish List:

1) Simulator directives
