IBIS Macromodel Task Group

Meeting date: 26 October 2010

Members (asterisk for those attending):
Agilent:                    * Fangyi Rao
                            * Radek Biernacki
Ansoft:                       Chris Herrick
                            * Danil Kirsanov
Cadence Design Systems:       Terry Jernberg
                            * Ambrish Varma
Celsionix:                    Kellee Crisafulli
Cisco Systems:              * Mike LaBonte
                              Stephen Scearce
Ericsson:                     Anders Ekholm
Intel:                        Michael Mirmak
LSI Logic:                    Wenyi Jin
Mentor Graphics:            * John Angulo
                              Vladimir Dmitriev-Zdorov
                              Zhen Mu
                            * Arpad Muranyi
Micron Technology:          * Randy Wolff
Nokia-Siemens Networks:     * Eckhard Lenski
Sigrity:                      Brad Brim
                              Kumar Keshavan
                            * Ken Willis
SiSoft:                     * Walter Katz
                              Mike Steinberger
                            * Todd Westerhoff
ST Micro:                     Syed Sadeghi
Teraspeed Consulting Group: * Scott McMorrow
                            * Bob Ross
Vitesse Semiconductor:        Eric Sweetman
Xilinx:                       Mustansir Fanaswalla

The meeting was lead by Arpad Muranyi

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Opens:

Arpad: Our task list gives us a lot of agenda items
  - Would like to reserve 20 minutes at end for BIRD

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Call for patent disclosure:

- none

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Review of ARs:

- Walter divide BIRD 119 into 4 separate BIRDs
  - Done BIRDs 121-124 have been submitted to the Open Forum

- Arpad change Typos BIRD to say the Typ is the implicit default for all types
  - Done

- Arpad and Walter discuss parameter Default/Value examples
  - Done

- Arpad address BIRD 114.2 escape sequences in strings
  - Done

- Arpad:  Write parameter passing syntax proposal (BIRD draft)
          for  -AMS models in IBIS that is consistent with the
          parameter passing syntax of the AMI models
  - Done, BIRD 117 & 118 submitted

- TBD:    Propose a parameter passing syntax for the SPICE
          - [External ...] also?
  - Done, BIRD 117 & 118 submitted

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New Discussion:

Arpad showed the changed Typos BIRD:
- New note explains Usage Out/InOut
  - Phrase about Model Specific parameters may not be clear
- Walter: The model maker may want to report back some internal data
  - The EDA tool should report it
- Arpad: That is already clear
- Arpad deleted the phrase
- New text explains tree data structure
- Optional keywords like Format now explained with one general example
  - Other examples follow same notation style

Task list item 4a: ambiguity between Format and Text
- No comment

Task list item 4b: Format = Table is invalid
- Walter: We should defer the discussion on Table
  - The Jitter BIRD may want to use Table
  - We will understand Table better at that time

Task list item 4c: Leaf syntax
- "-50" as example of leaf name is confusing because it looks like a number
- Walter: This is correct

AMI_Version BIRD discussion:
- Walter: An existing 5.0 IBIS file can convert to 5.1 without requiring
  any changes to AMI files that it references
- Radek: Agree
- Walter: Sections 6 and 10 will be a maintenance nightmare if we keep them in
  IBIS
- Fangyi: Why not integrate this with IBIS version?
- Todd: The IBIS and AMI files are a matched set
- Ken: It will be hard to remember what works together
- Radek: There is no reason to have a separate version field if it is part
  of the IBIS spec
- Arpad: In 5.1 we would only be able to reference new AMI files
- Radek: It could say "same or lower version"
- Todd: We are making this more complicated than it needs to be
- Arpad: So IBIS 5.1 does not need to use older AMI models?
- Ken: We could have IBIS_Ver in the AMI file
- Walter: Then changing it in the IBIS file means changing all referenced
  files

Walter showed BIRD 121:
- Supporting_Files is a simple list of files
- DLLPath gives places where DLLs might be found
- Fangyi: It should be stated what EDA tools do with it
- Ken: Do they have to be in the same directory?
- Walter: It can be relative, below the current directory
- Mike: Are forward slashes specified?
- Walter: Yes
- DLLid is needed when the same DLL is used more than once
- Mike: DLLPath and DLLid should be DLL_Path and DLL_Id
- Walter: These spellings are already in use in Opal
- Samples_Per_Bit may be needed
- Walter: Some models only work at one rate
- Scott: That is out of place in this BIRD
  - This BIRD is about how to get the simulator working with files
- Todd: We can rename the BIRD

Walter showed BIRD 122:
- This is about Equivalent-Circuit Analog Model parameters
- Single ended output has to be converted to differential
- Step response to input of TX can be differentiated to get impulse response
- Vendors do not want to disclose their circuits, not even the interconnect
- The partition between analog and algorithmic portions is important
- This does not handle common mode, but that is a general AMI problem

Scott showed Circuit and Algorithmic Modeling:
- SerDes can be separated into circuit and algorithmic models
- BIRD 119 clouds the boundary
- We need flexibility to model next generations of serdes
- IP vendors want to hide their IP
- Most vendors use a Matlab type of environment
- Some of the approximations are not correct
- There are inappropriate uses of AMI for analog modeling
- A long list of things need to be discussed
- What is the appropriate model for each type of architecture?
- A model maker can easily oversimplify
- Would rather have a generalized model than a template model
  - Maybe a SPICE-like circuit language would be best
- Fangyi: The analog model in BIRD 119 belongs in IBIS, not AMI
- Walter: The presentation is correct, with good issues
  - BIRD 119 reflects how IC vendors are currently partitioning
  - Except that Noise/Jitter is in BIRD 119
- Todd: The boundary was never well defined
  - We are trying to get to 10Gb/s
- Fangyi: Some models give different results when terminations change
  - Touchstone can't be renormalized to any impedance, for example
- Scott: The termination is usually in the s-param
- Todd: This is working today with touchstone
- Ken: Why would we go back to rigid templates?
- Todd: Vendors will not want to give clear text circuits
- Scott: Even the touchstone part of BIRD 119 is not well defined
- Arpad: We need to see what we can achieve with BIRD 119
- Scott: Peaking coils are in many shipping devices
  - We need to get that right
- Walter: Can they be represented with touchstone?
- Scott: As long as the boundary is defined correctly
  - It's not clear what the s-param interface represents
- Arpad: Is this a new BIRD?
- Todd: We need more technical discussion
- Scott: The template codified in the spec is what people use
- Walter: People need to ship models today
- Arpad: The BIRDs already submitted should help with that
- Walter: The parameters belong in the AMI file
  - The question is where the template belongs
- Fangyi: Can we extend corners to the dependency table?
- Arpad: Even with my BIRDs we would have to write about boundaries

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Next meeting: 02 November 2010 12:00pm PT

Next agenda:
- BIRD 119
- Any other new BIRDs

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IBIS Interconnect SPICE Wish List:

1) Simulator directives

