IBIS Macromodel Task Group

Meeting date: 19 May 2015

Members (asterisk for those attending):
ANSYS:                      * Dan Dvorscak
                            * Curtis Clark
Avago (LSI)                   Xingdong Dai
                            * Bob Miller
Cadence Design Systems:       Ambrish Varma
                              Brad Brim
                              Kumar Keshavan
                              Ken Willis
eASIC                       * David Banas
                              Marc Kowalski
Ericsson:                     Anders Ekholm
IBM                           Steve Parker
Intel:                      * Michael Mirmak
Keysight Technologies:      * Fangyi Rao
                            * Radek Biernacki
                            * Nicholas Tzou
Maxim Integrated Products:    Hassan Rafat
Mentor Graphics:            * John Angulo
                            * Arpad Muranyi
Micron Technology:            Randy Wolff
                              Justin Butterfield
QLogic Corp.                  James Zhou
                              Andy Joy
SiSoft:                     * Walter Katz
                              Todd Westerhoff
                            * Mike LaBonte
Synopsys                      Rita Horner
Teraspeed Consulting Group:   Scott McMorrow
Teraspeed Labs:             * Bob Ross
TI:                           Alfred Chong

(Note: Agilent has changed to Keysight)

The meeting was led by Arpad Muranyi.

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Opens:

- Arpad: Should we discuss [Initial Delay]?
  - Michael M: Not yet, there will be a BIRD.
- Radek: We tabled [Define Package Model] but could discuss the changes made.
  - What are the differences between the one we approved and what Open Forum will vote on?

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Call for patent disclosure:

- None


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Review of ARs:

- Arpad to review IBIS specification for min max issues.
  - In progress.


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New Discussion:

Directionality BIRD draft

- Michael M: Have all issues been resolved?
- Bob M: I had asked some questions but they may be academic.
  - The problem we are trying to solve is not clear.
- Arpad: AMI models do not say if they are TX or RX.
  - There is no way to check if they are assigned incorrectly.
- Michael M: It's not much of an issue if they work only in one direction.
  - AMI parameters can be used to check them in that case.
  - But AMI can be used for bidirectional DDR4 signals, for example.
- Bob M: A bidirectional SerDes that does turnaround makes no sense.
- Michael M: Only the current state would be given, no dynamic turnaround.

- Bob M: In EDA tools I assign models explicitly to TX or RX.
  - A single executable that can be TX or RX should be possible.
- Michael M: Users don't want to copy a topology just to model the reverse direction.
  - The BIRD supports single executables, but separate AMI files are required.
- Walter: IBIS describes parts and must describe the behavior of each pin.
  - If a pin is I/O then IBIS must be able to describe both behaviors.

- Arpad: We were going to check direction by Reserved_Parameters.
  - There are few required parameters, we may not have enough for checking.
- Walter: The model writer can add an In Model_Specific parameter that the model checks.
- John: A Reserved_parameter would not require that kind of user intervention.
- Arpad: We could require a Reserved_Parameter for model direction.
- Walter: We would define TX AMI files and RX AMI files.
- Radek: A Model_Specific parameter would clarify this.
- Walter: It would be of type Value.
- Bob R: For I/O models it's unclear.
- Walter: There are separate AMI files.
- John: Each model would look for a parameter of a certain name.
- Bob R: The EDA tool doesn't need to know it, only the model.

- Arpad: Is this BIRD ready for submission?
- Bob R: We left the Reserved_Parameters in it.
- Walter: Michael M should issue a clean final draft and we can vote on it next week.
- Bob R: How would we identify the TX and RX Executable lines?
- Radek: There is a parameter for that in the IBIS file.

- Michael M showed the BIRD.
- Michael M: It is a subparameter of the [Algorithmic Model] keyword.
  - There are no Reserved_Parameters defined in the BIRD at all.
  - There is however a table listing known TX and RX Reserved_Parameters.

- David: How do we use one DLL for I and O?
- Michael M: It is called from one [Algorithmic Model] with Direction TX and one with Direction RX.
- Bob R: Can a single DLL be used for multiple models?
- Radek: We removed that restriction.
- Michael M showed the removed phrase.
- Michael M: This was done so existing models don't have to change much.
  - Direction is not required except for I/O Model_types.

- David: Can there be multiple Directions in one section?
- Walter: There could be Executable_TX and Executable_RX instead of the Direction subparameter.
- David: A field right on the line would be consistent with information.

- Arpad: We still need to resolve if multiple TXs and RXs are allowed for one [Algorithmic Model].
- Walter: We already do, for platforms.
- Bob R: Only one Direction subparameter should be in one [Algorithmic Model].

- John: There could be a risk with having multiple [Algorithmic Model] sections.
- Michael M: Each [Algorithmic Model] should point to one AMI file.
  - Doing it this way we can check for that.
  - Cadence liked this syntax better.

- Arpad: Can we have two [Algorithmic Model] section with the same Direction?
- David: Could there be subparameter hierarchy?
- Michael M: I don't think we have any examples of that so far.
- Arpad: We have hierarchical keywords.

- Mike L: This will require one AMI file per [Algorithmic Model] block?
  - We have not had that rule so far.
- Michael M: Yes.
- Mike L: I know of no models that use different AMI files so far.
  - Software would be easier to write with this assumption.
- Bob R: The example in this BIRD has different AMI file names for TX and RX.
  - It's not clear.
- David: It's clear, the question is what we want.
- Mike L: Some models have platform dependent Supporting_Files.
  - They might want to use separate AMI files for each platform.
- David: So there have to be unique TX and RX AMI files, but there could be more than two files.

- Radek: Do we currently disallow multiple [Algorithmic Model] keywords?
- Michael M: Yes, that changes in this BIRD.

AR: Michael M email list to start discussion of new Directionality issues.


Problems with Global Ground in IBIS:

- Arpad: We only have time for a short introduction.
- Walter showed a presentation "Terminal Names in IBIS".
- Walter: There is confusion over what a terminal name is.
  - It is about voltage references.
  - C_comp is involved.
  - Some of our figures have ground symbols.
  - We made an editorial error while going from IBIS 5.0 to 5.1.
  - We should replace some terminal names in diagrams with standard names like A_pcref.
  - The references for IV curves must be discussed, some use a mythical ground.
  - It would be best to use C_comp_power_clamp and C_comp_ground_clamp instead of C_comp.
- Arpad: Will this be discussed in the interconn meeting tomorrow?
- Walter: It should be.

AR: Walter send "Terminal Names in IBIS" presentation to Mike L for posting.


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Next meeting: 26 May 2015 12:00pm PT
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IBIS Interconnect SPICE Wish List:

1) Simulator directives
