IBIS Macromodel Task Group

Meeting date:25 May 2021

Members (asterisk for those attending):
Achronix Semiconductor        Hansel Dsilva
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:
  
- None.

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Review of ARs:

- Walter to send out BIRD211.2_draft8.
  - Done.

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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 May 18th
meeting.  Walter moved to approve the minutes.  Randy seconded the motion.
There were no objections.

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New Discussion:

BIRD211.2 draft 8:
Arpad noted that several emails had been exchanged on the ATM meeting list since
the last meeting.  Walter said that Bob had proposed a substantive change to the
BIRD.  With Bob's proposed language, the new Tx_Impulse_Input parameter would
only apply to Redriver Txs.  The parameter would not apply to all Tx models.

Arpad asked why Walter wanted to apply it to all Tx models.  Radek said it had
been in response to a comment he had made.  He said Walter's initial proposal
introduced the new parameter for Redriver Txs only.  Radek had stated that this
would create two different types of Tx model, so Walter had made it applicable
to all Tx models instead.  The new parameter is needed for Redrivers, but the
Redriver Tx model need not be different from other Tx models.

With regard to Bob's proposal, Walter asked, "Why not allows this for all Txs?"
Bob said that he had kept it open to apply to Retimers too (i.e., all repeaters)
because the BIRD modifies the Retimer flow too, even though the new flow figures
(block diagrams) are only in the Redriver section.  Bob said he thought the four
value choices for the new parameter were moot if the Tx isn't part of a
repeater.  Bob said his proposal is that for version 7.1 and above, if
Tx_Impulse_Input is declared then the Repeater_Type is also required.  He did
not want to carry over an implied legacy flow (the corrected flow corresponding
to the "Downstream" setting of the new parameter), and he wanted the model maker
to explicitly declare what the setting/flow is for models beyond 7.1.  Curtis
noted that Bob's proposed language also included coupling to the [Repeater Pin]
IBIS keyword.  He said that this language had also been used in the IBIS 7.0
specification, but it wasn't correct to require an AMI model parameter, in this
case Tx_Impulse_Input, if the [Component] level keyword [Repeater Pin] were
used.  There could be AMI models that had nothing to do with any of the
[Repeater Pin] entries.

Arpad said his understand was that we are just trying to fix the flow for
Redrivers.  For Retimers the channels are independent, so why are we touching
the Retimer flow?  Walter said he had re-written the normal (single-channel),
Redriver, and Retimer flows.  He had rewritten them to allow the application
of this new parameter to any Tx in any of the flows.  Walter said to keep it
general, all Txs could specify any of the new parameter's four values to
specify their input.  Arpad asked if we would now be adding requirements on
terminal models that don't need Redriver related changes.  Walter said we
are not.  He said the parameter is optional, and the default behavior is the
normal legacy behavior.

Fangyi summarized: for a terminal (initial) Tx, the "Downstream" and "Combined"
options would be the same (legacy behavior),  "Separate" would be a new option,
and "Upstream" would mean the unit impulse response is the input to the Tx.

Bob said he thought the current BIRD's changes were confusing.  Ambrish said
that if we think it's confusing, how's it going to be for everyone else?
Ambrish said he thought we should just fix the Redriver statistical flow, which
is the only thing that needs fixing.  He said this proposal is changing a lot of
text, and he asked if we could restrict it to just fixing the Redriver
statistical flow.  Fangyi said he thought this was possible.

Walter said that if someone wants to make a motion that says that
Tx_Impulse_Input is only allowed when the Tx is part of a repeater, then they
should do it so we can vote on it.  Fangyi said if we agree on Ambrish's
proposal to restrict changes to the repeater flows, then Bob's proposal was one
way to accomplish this.  Ambrish agreed.

Ambrish moved to restrict the changes to the repeater flows.  Bob seconded.
Curtis commented that he was reluctant to give up on Radek/Walter's idea of
keeping the parameter generally applicable to all Txs, which meant it would
affect other flows.  Walter objected to the motion and asked for a roll call
vote.  The roll call vote tally was:
Ansys - No
Cadence - Yes
Keysight - Abstain
Micron - Abstain
Siemens - Abstain
SiSoft - No
Teraspeed - Yes

The roll call vote concluded with a vote tally of Yes – 2, No – 2, Abstain – 3.
The vote did not pass.

Discussion continued.  Walter said he had rewritten the text for the normal
reference flow as well as the repeater flows.  However, IBIS 7.0 only has
diagrams of the repeater flows, so he only created diagrams for the repeater
flows given the values of the new parameter.  He said it would be helpful if he
added flow diagrams for the normal reference flow.  Randy asked Walter to also
add a statement referencing "Downstream" to the normal flow.

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

AR: Walter to add diagrams for the normal reference flow and send out
    BIRD211.2_draft9.

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Next meeting: 01 June 2021 12:00pm PT
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IBIS Interconnect SPICE Wish List:

1) Simulator directives
