                                             
IBIS Macromodel Task Group

Meeting date: 13 Dec 2011

Members (asterisk for those attending):
Agilent:                      Fangyi Rao
                              Radek Biernacki
Altera:                     * David Banas
Ansys:                        Samuel Mertens
                            * Dan Dvorscak
                            * Curtis Clark
Arrow Electronics:            Ian Dodd
Cadence Design Systems:       Terry Jernberg
                            * Ambrish Varma
			    * Feras Al-Hawari
Celsionix:                    Kellee Crisafulli
Cisco Systems:                Ashwin Vasudevan
                              Syed Huq
Ericsson:                     Anders Ekholm
IBM:                          Greg Edlund
Intel:                        Michael Mirmak
LSI Logic:                    Wenyi Jin
Maxim Integrated Products:  * Mahbubul Bari
Mentor Graphics:            * John Angulo
                              Zhen Mu
                            * Arpad Muranyi
                            * Vladimir Dmitriev-Zdorov
Micron Technology:            Randy Wolff
NetLogic Microsystems:        Ryan Couts
Nokia-Siemens Networks:     * Eckhard Lenski
QLogic Corp.                * James Zhou
Sigrity:                      Brad Brim
                              Kumar Keshavan
                            * Ken Willis
SiSoft:                     * Walter Katz
                              Todd Westerhoff
                              Doug Burns
			    * Mike LaBonte
Snowbush IP:                  Marcus Van Ierssel
ST Micro:                     Syed Sadeghi
Teraspeed Consulting Group:   Scott McMorrow
                            * Bob Ross
TI:                           Casey Morrison
                              Alfred Chong
Vitesse Semiconductor:        Eric Sweetman
Xilinx:                       Mustansir Fanaswalla

The meeting was lead by Arpad Muranyi

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Opens:

- Arpad: The next meetings will be Dec 20 and Jan 3 2012

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Call for patent disclosure:

- None

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Review of ARs:

- Ken propose reduced set of jitter parameters
  - Nothing formal yet
  - Have been discussions
  - May be some discussion today
  - Mostly on the RX side

- David write mathematical description of combined Dj proposal
  - On hold, pending further discussion

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New Discussion:

David motioned to discuss BIRD 123:
- Walter seconded
- No one opposed

Discussion of BIRD 123:
- Walter showed an email discussing BIRD 123
- Walter: It should be clear once we go through the derivation methods
  - Model defines parameters for Rj, Sj, DCD not modeled in clock_times
  - Also defines *_Clock_Recovery_* for what is modeled
  - These describe when the EDA tool needs to handle jitter separately
  - Using only Init EDA tool must determine center of eye
  - This is the only part not well defined
  - It should be based on the median of the PDF
- David: It might be the center between the two medians
- Vladimir: Median is not the mean
  - It is difficult to find the median
- Walter: It should not be difficult in time domain
- David: It would be the peak of a fairly wide averaging window
- Walter: If we use the mean that would have to be carefully defined
- Arpad: One definition uses the mode, the most prevalent value
- Walter: That would not be the best choice

- Ken: These parameters are not needed if all jitter is modeled
- Walter: True
- Ken: We should have one parameter set regardless of whether Init or Getwave is used
- Walter: Every one of these parameters has been required by a vendor
  - It's hard to put Rj into clock_times
- Ken: Rj is usually handled by the tool
- Walter: What if the model does include Rj in clock_times?
- Ken: We should be able to do it with less parameters
- Ambrish: This allows jitter to be double counted
- Walter: The model explicitly say what jitter to add
- Ambrish: The user may want to add more jitter
- Walter: They still can do that

- Arpad: These are Reserved Usage In parameters?
- Walter: They are Info, not In
  - There is a separate discussion whether to allow Out
  - No objection to not allowing Out
  - In IBIS 5.0 TX jitter was allowed to be Out
- Arpad: Was that an oversight?
- Walter: It was thought to be a need at the time
  - It is not needed
- David: I proposed making them Out to cut the number of parameters
- Walter: How would it do that?
- David: We have two sets of parameters in Walter's proposal
- Walter: One is for when you have clock_times, one for not
  - With a forwarded clock the jitter is not known by the model
  - That has to be added
  - It helps to keep the parameters separate
  - One example implementation is a rotator
    - Each rotator generates a base frequency
    - The CDR switches from one rotator to another
    - The frequency is different from the TX
  - Another is forwarded clocks
    - The frequency is the same as the TX
- Ken: This is driven by the need to model external clocks?
- Walter: It does not depend on whether you have a forwarded clock
- Arpad: How does it get into the RX DLL?
- Walter: It does not, it is in the AMI parameters
- Arpad: The RX never needs to get it from outside?
- Walter: We decided that would be in a separate BIRD
  - There will be additional mechanisms to model spectral density jitter

- Arpad: How does this relate to the other drafts?
- Walter: This explains the BIRD I posted
  - That one should agree with this
  - The only exception is adding the eye center definition
  - I will review the BIRD and email to the reflector
- Arpad: Hopefully people will review and we can vote in January
- Bob: We should post the derivation explanation somewhere

AR: Walter update BIRD 123
AR: Walter create jitter derivation document

- Ken: Did we agree they are Info?
- Walter: The only one that should be Out is RX Noise
  - RX Getwave changes the gain and can affect Noise

- Ken: Will we deprecate TX Jitter?
- Walter: That can be converted to these parameters
  - Existing models us it
  - Deprecation begins with a warning announcement
- David: If the DFE adapts maybe these should be Out
- Mike: A model might not jitter clock_times depending on the controls
- Walter: A dependency table can describe that
- Arpad: The BIRD does out describe what the tool does if it is an Out
  - The model can specify jitter but the tool might ignore that
- Walter: The tool should use the model value as default

- Ken: Is there a reason to make it Out?
- David: It is risky to assume updates will never be needed
- Walter: With RX Noise there is a known reason
- David: Our model might want to tell the tool how much jitter to add
- Walter: Ambrish objected to TX jitter being an Out
  - That has to be injected back into the stimulus
  - It gets complicated and should be avoided
  - We have no request from an IC vendor yet
- Arpad: It is usually safer to have less features and add later
- We agreed it would be Info

- Vladimir: Why not add noise to the waveform?
- Walter: You could
- This would avoid using Out mode
- Walter: Except Gaussian noise has tails
  - There are ways to handle it after the AGC converges
  - Some models do this and are not standard
  - IC vendor will like the option to have it as an Out
- Vladimir: We can use the last value as long as it is Stable

- Ambrish: There are different kinds of jitter for statistical and TD
  - There could be an overlap in the kinds of jitter
- Walter: It is up to the EDA tool

Meeting ended.

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Next meeting: 20 Dec 2011 12:00pm PT

Next agenda:
1) Task list item discussions

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IBIS Interconnect SPICE Wish List:

1) Simulator directives

