IBIS Macromodel Task Group

Meeting date: 31 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: Would like to discuss a package modeling topic.


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Call for patent disclosure:

- None


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Review of ARs:

- Michael M update AMI Directionality BIRD
  - no report.

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


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New Discussion:

PAM4 BIRD:

- Walter: We have an updated PAM4 BIRD to send out.


Package modeling:

- Arpad: We have new package formats but the legacy formats might still be used.
- Arpad showed a presentation.
- slide 1:
  - Arpad: This is without [Pin Mapping].
    - The inductors might not be present.
    - In case 1 there might be [Package] or [Pin] RLC only.
    - In case 2 there is a [Define Package Model]
    - In case 3 the [Define Package Model] does not define some pins.
    - In that case should the unmodeled pins use other mechanisms?
    - Or should it be a short?
    - There is no information on how power and ground pins are connected.
    - Signal models should come form the package or pin.
- slide 2:
  - Arpad: This shows [Pin Mapping] shorting pads together.
    - Some inductors might get shunted together if the pins are also shorted together.
    - The question remains, how should unmodeled pins be handled?
    - Merging parasitics into one pin might make sense.
    - The specification does not say how to create this model.
- slide 3:
  - Arpad: This shows power and ground pins not defined in [Define Package Model]
    - Maybe the [Pin] RLC or [Package]should be used.
    - Using a short is a possibility.
    - That would create some"packageless" pins.
    - The pins could be shorted together.
    - Without a combined model that will not work.
- slide 4:
  - Arpad: Not all power and ground pads are shorted here.
    - The spec doesn't tell us what to do.
    - Those other pins can't be simulated anyway.
- slide 5:
  - Arpad: This is from Randy's presentation.
  - Randy: You may get ports lumped into a single capacitance.
    - To make matrices the same size a lot of post-processing would be needed.
    - That might be error prone.
- slide 6:
  - Randy: Without [Define Package Model] there is a question how to split up capacitance.
    - With just [Package] it usually represents only signal pins.
- slide 7:
  - Arpad: Only a complete [Define Package Model] is correct for PI.
    - Merging parasitics would be desirable,but how will simulators deal with it?
    - This might be worthwhile because there probably will be more legacy models.
    - We would need to have this in the specification.
  - Bob: It would have to be clear to users that only 1 power and 1 ground would be used.
  - Arpad: Agree, the BIRD hopefully captures that.

- Arpad showed a draft BIRD "Power Pin Package Modeling"
- Arpad: The analysis part is similar to the slides.
  - No name yet for the new sub-parameter under [Pin Numbers].
  - One paragraph becomes several paragraphs.
  - The "as many names as" clause has been clarified.
  - That needs to match the original intent of the spec.
- Mike: The order of hierarchy might be more explicit here.
- Arpad: For missing pins it states "may be merged", it's not required.
- Radek: It should be more precise than "may" or "should".
- Arpad: The sub-parameter tells the tool there is a merging pin.
  - The sub-parameter is followed by a list of pin names.
  - They have to be in [Pin] and have to be power or ground pins.
  - Without [Pin Mapping] PI can not be analyzed.
  - There are invalid combinations.
  - With [Number of Sections] the new sub-parameter is not allowed.
  - Randy said that is likely only with matrix formats.
  - The other sub-parameters are allowed only when the new one is absent.
  - There are other rules about names and buses.
  - Pin names may span lines, but each line starts with the new sub-parameter.
  - It may list only pin names not in [Pin Numbers].
  - The EDA tool must short those pins to eliminate the possibility of disconnected pins.
  - Undefined pins must be disconnected.

- Radek: Does it have to be exhaustive or a subset of [Pin Mapping]?
- Arpad showed IBIS 6.0.
- Arpad: You still can have a mixed case.
- Bob: There is a question if we want that rule.
- Radek: We might have unusual groupings.
  - What happens to pins not specified in [Pin Numbers]?
- Arpad: We could have a requirement for that.
- Randy: Agree, we could check for that.
- Bob: I would prefer a new keyword like [Merged Pin Numbers].
- Arpad: The merged pin would list the pins it merges.
  - This compact.
  - A new keyword might make it harder to see what is merged.
- Bob: It does not apply to the uncoupled case.
- Walter: Presumably Micron has models that tools don;t know how to handle.
- Randy: Yes.
- Walter: It would help to see the IBIS file as an example.
- Randy: OK.
- Walter: Will those models be converted to new formats?
- Randy: We have old models that will not change.

- Curtis: This BIRD defines a way to address the ambiguity, but there will
  still be older models out there.
  - Do we need to clarify how we expect things to be handled in these situations
    with older models?
- Randy: We might look at going back and updating our older models.
- Walter: We introduce the BIRD, and for older models we assume user documentation
  or some other source explains what the model expects.

- Arpad: There is a question which version update this might go into.
  - It could go to editorial to get it in sooner.
- Bob: I'm not sure the sub-parameter is needed.
  - The buses might be merged by rules.
- Arpad: That may be true, I need to consider that.

AR: Randy provide example for new package BIRD draft.

AR: Arpad send draft package BIRD to Mike for posting.

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Next meeting: 07 Apr 2015 12:00pm PT
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IBIS Interconnect SPICE Wish List:

1) Simulator directives
