IBIS Macromodel Task Group

Meeting date: 24 March 2015

Members (asterisk for those attending):
Altera:                       David Banas
ANSYS:                        Dan Dvorscak
                            * Curtis Clark
Avago (LSI)                   Xingdong Dai
Cadence Design Systems:     * Ambrish Varma
                              Brad Brim
                              Kumar Keshavan
                              Ken Willis
eASIC                         David Banas
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
eASIC                         Marc Kowalski
SiSoft:                     * Walter Katz
                            * Todd Westerhoff
                            * Mike LaBonte
Synopsys                      Rita Horner
Teraspeed Consulting Group:   Scott McMorrow
Teraspeed Labs:             * Bob Ross

(Note: Agilent has changed to Keysight)

The meeting was led by Arpad Muranyi.

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Opens:

- Arpad: I have a spec clarification issue.


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Call for patent disclosure:

- None


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Review of ARs:

- Michael M update AMI Directionality BIRD
  - Arpad: He reported this is in progress.

- Walter and Randy produce C_comp BIRD.
  - Randy: Some progress, but we need to resolve issues about parameters.

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


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New Discussion:

PAM4 BIRD:

- Walter: Thanks to all who submitted comments.
  - A list will be allowed to select NRZ or PAM4.
  - There will be upper and lower timing offsets.
  - The tool returns an impulse or waveforms, not an eye.
  - Duobinary is a question.
  - The keywords are named to not conflict later.
- Arpad: Should we number the thresholds?
- Walter: We called them PAM4_Upper, PAM4_Lower, PAM4_Center.
  - Each scheme could have its own names.
- Mike: If NRZ and PAM4 are selectable, numbered thresholds might conflict.
- Walter: We should not have Duobinary until it is in use.
- Fangyi: Agree with Walter.
  - An IC vendor suggested we use Rx_Clock_Recovery_Mean for the middle eye.
- Walter: In GetWave we get center eye clock_ticks.
  - Offset would be better for that.
  - For statistical would be offset from the mean.
- Fangyi: In TD offset is from the mean.
- Walter: SO we have upper and lower eye mean?
- Fangyi: In statistical it would be offset from the recovered clock.
- Walter: If the mean is 10ps from center, by default I use
  - Normally there is only one clock for all 3 latches.
  - There is no offset in time domain, you use clock ticks.
  - A PAM4 has only one clock recovery.
  - Upper and lower may have different phases.
  - One offset for each segment should apply to TD and stat.
- Fangyi: So the offsets are added to the center mean?
- Walter: Yes.
- Fangyi: So clock_times is for the center eye.
  - A numbered scheme would complicate that.
- Todd: I like the idea of numbering the eyes.
- Arpad: We could have zero, positive, and negative numbers.
- Todd: We have to know which eye the clock_times pertain to.
- Walter: A lot of places use upper and lower.
  - If PAM5, PAM6, PAM7 were coming things would change.
- Mike:New modulations will have their own prefixes.

- Fangyi: We need to correct "bit time"
- Walter: Agree, it should be "symbol time".
- Fangyi: ?? should be an integer.
- Walter: Agree.



Co-optimization:

- Walter: No update for today.
  - We should avoid dynamic modulation switching.
  - We simulate at PHY level, not MAC.


C_comp:

- Randy: Curtis Clark sent comments.
  - I added nodes for a differential receiver.
  - Curtis had questions about how different simulators would handle it.
- Curtis: Walter said these models complicate extracting K(t).
  - Bob's presentation shows how to move the measurement point.
  - Maybe the K(t) should be in the IBIS file.
- Walter: The format would be simple.
  - There would be four curves.
  - Simulation would be easy.
  - This may be harder for model makers.
- Arpad: Without V-T tables verifying would be harder.
  - With the V-T load you should get the same waveform.
  - You could have both.
- Radek: They might not agree.
- Arpad: Tools derive K(t) already , why have model makers do it?
- Walter: C_comp makes it hard to get it right. 
- Curtis: Bob created a complicate system to get K(t).
- Walter: Tools reinvent K(t) every time they simulate.
- Mike: Wouldn't K(t) tables eliminate current differences among tools?
- Walter: Yes.
- Arpad: We should finalize the C_comp proposal before this.


- Arpad showed [Package] in the IBIS spec.
- Arpad: We have a series of overrides.
  - In [Define Package Model] [Pin Numbers] it does not say they all have to be in [Pin Names].
  - The [Package] might be a partial model.
  - The remaining pins might use defaults.
  - For example Power and GND pins could be omitted from [Pin Numbers].
  - The spec doesn't say what to do with them.
  - Tools handle this differently.
  - Some create a short, some leave it open.
- Mike: Can [Define Package Model] have both [Pin Numbers] and matrix formats?
- Bob: No they are mutually exclusive.
  - A missing [Define Package Model] pin would fall back to [Pin] RLC, then to [Package].
- Arpad: If no [Pin Mapping] there would be straightforward pin to pad paths.
  - Why describe 10 power pads when I can describe one and leave the rest disconnected.
  - That would rely on [Pin Mapping] to connect them.
  - It assumes shorts would not be created.
  - Some tools will create shorts though, eliminating the model.
- Bob: A rail might be shorted to nine other rails through buffers.
- Randy: I get this with my models.
  - With a power plane 10 balls are connected to the package.
  - We shorted the powers together, same for grounds.
  - In [Pin Mapping] all 10 pins are there but the package model has only one.

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Next meeting: 24 Mar 2015 12:00pm PT
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IBIS Interconnect SPICE Wish List:

1) Simulator directives