Minutes from the 05 March ibis-atm meeting are attached.
The following documents, which were discussed during the meeting, have been
posted to the ATM Task Group archive.
*DATE* AUTHOR <http://ibis.org/atm_wip/archive-author.html> ORGANIZATION
<http://ibis.org/atm_wip/archive-org.html> TITLE
<http://ibis.org/atm_wip/archive-title.html> FORMATS
05-MAR-2019 Randy Wolff Micron Technology C_comp Model Using IBIS-ISS or
Touchstone BIRD draft 3_5_2019 (zip
<http://ibis.org/atm_wip/archive/20190305/randywolff/C_comp_Model_Using_IBIS-ISS_or_Touchstone_BIRD_draft_3_5_2019.zip>
)(dir
<http://ibis.org/atm_wip/archive/20190305/randywolff/C_comp%20Model%20Using%20IBIS-ISS%20or%20Touchstone%20BIRD%20draft%203_5_2019/>
)
26-FEB-2019 Arpad Muranyi Mentor, A Siemens Business Rx_Receiver_Sensitivity
BIRD draft_2 (zip
<http://ibis.org/atm_wip/archive/20190226/arpadmuranyi/Rx_Receiver_Sensitivity_BIRD_draft_2.zip>
)(docx
<http://ibis.org/atm_wip/archive/20190226/arpadmuranyi/Rx_Receiver_Sensitivity%20BIRD%20draft_2/BIRDxxx_draft_2.docx>
)
IBIS Macromodel Task Group
Meeting date: 05 March 2019
Members (asterisk for those attending):
ANSYS: Dan Dvorscak
* Curtis Clark
Cadence Design Systems: * Ambrish Varma
Brad Brim
Kumar Keshavan
Ken Willis
eASIC: David Banas
GlobalFoundries: Steve Parker
IBM Luis Armenta
Trevor Timpane
Intel: Michael Mirmak
Keysight Technologies: Fangyi Rao
* Radek Biernacki
Ming Yan
Stephen Slater
Maziar Farahmand
Mentor, A Siemens Business: John Angulo
* Arpad Muranyi
Micron Technology: * Randy Wolff
Justin Butterfield
SiSoft (Mathworks): Walter Katz
* Mike LaBonte
SPISim: Wei-hsing Huang
Synopsys: Rita Horner
Kevin Li
Teraspeed Consulting Group: Scott McMorrow
Teraspeed Labs: * Bob Ross
The meeting was led by Arpad Muranyi. Curtis Clark took the minutes.
--------------------------------------------------------------------------------
Opens:
- None.
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Review of ARs:
- Randy to investigate if/why/how a clock waveform input might be used.
- In progress.
- Michael M. to investigate if/why/how a clock waveform input might be used.
- In progress.
- Michael M. to check with IP experts on whether DC_Offset is useful for Tx.
- In progress.
- Mike L. to reach out to FEC presentation authors for more information.
- In progress. Mike said that he had emailed three people and heard back from
two of them. The two responses contained widely differing opinions. One
suggested, "yes, if we had a new function we could use this to do some kind
of analysis and FEC reporting." The other respondent said, "That's not
going to work. There are some issues with the presumptions behind those
calculations." Mike noted that a model maker can prototype this already,
perhaps using the AMI_Close() function, as we had discussed in previous
meetings. He noted that no one is waiting on this functionality at this
time. Therefore, he suggested we should take no action on this topic until
someone comes to us. Arpad noted that he had some concerns if we suggested
that AMI_Close() could be used to provide the functionality. In the past
there was discussion of avoiding overloading AMI_Init(), and doing extra
things in AMI_Close() could cause similar confusion. Arpad noted that there
was no need to discuss this issue now, but he wanted to make the point.
Mike agreed, and said some models violate the limited scope of AMI_Close().
Curtis asked if this topic should be removed from the Topic bin list. Arpad
and Mike agreed that it should.
- Arpad to send draft_2 of the Rx_Receiver_Sensitivity clarification BIRD to the
ATM list.
- Done.
--------------------------
Call for patent disclosure:
- None.
-------------------------
Review of Meeting Minutes:
Arpad asked for any comments or corrections to the minutes of the February 26
meeting. Mike L. moved to approve the minutes. Randy seconded the motion.
There were no objections.
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New Discussion:
Rx_Receiver_Sensitivity BIRD draft_2:
Arpad noted that he had sent out draft_2, and it is posted in the ATM archives.
He said he would do nothing further with this until IBIS 7.0 is approved, then
he will update the draft relative to IBIS 7.0.
Enhanced C_Comp:
Randy reviewed his latest draft and noted:
- Tried to simplify things relative to the last draft.
- Decided that supporting series elements was too complex for the C_comp
proposal.
- We have BIRD189 that allows us to model on-die interconnect that way.
- Avoid the complexities of removing the effects of series resistance when
simulating the C_comp model.
- Also removed the "differential" C_comp model.
- Didn't want to allow true differential C_comp modeling with this proposal,
as it might have unintentionally broken some simulator algorithms.
- Simplified for single-ended or pseudo-differential ([Diff Pin] pairs).
Arpad noted that [External Model] is currently the only way to do true
differential. The model maker would likely build all their C_comp modeling into
the [External Model], and C_comp keywords are ignored when [External Model] is
used.
Randy continued:
- Left in the description of an internal node that can be used to probe at the
input buffer. Available in case the C_comp model includes a
filtering circuit between the Buffer I/O terminal and the input buffer.
Radek noted the phrase "voltage dependencies" at the end of the "Definition of
the Issue" paragraph. He asked if that was intended to include non-linearities.
Randy said this proposal was intended to allow anything you can do with IBIS-ISS
syntax. Radek said we might consider modifying that language later.
Randy continued:
- Removed lots of language related to the series elements and the additional
terminal names related to them.
- Other Notes: section now includes a more complete description of the extra
input buffer probing location. There was also confusion with the last
draft about where clamp data would be. This explains that all the clamp
data exists at the Buffer I/O terminal and not anywhere else.
- Made sure Terminal_Number, File_IBIS-ISS, etc., use the exact same language
as BIRD189.
- There are now many fewer Terminal_Types because differential terminals and
the Buffer_O node are no longer in the proposal.
Bob noted the statement that IBIS-ISS subcircuit terminals "shall not contain an
ideal reference node (SPICE node 0 or its synonyms)". Randy said that in last
year's discussions we decided we wanted someone to choose one of the existing
references in the scope of the [Model]. Bob said A_gnd can be a reference
terminal in a BIRD189 interconnect model, and we might want to revisit that
language.
Arpad noted that since this draft duplicates so much of the text from BIRD189,
we might be better off with an up-front section explaining the rules. Then the
section could be referred to in multiple places. Randy noted that there were
some minor differences, such as the minimum Number_of_Terminals, so while much
of the text was common it might not be easy to break out a single section that
applied to BIRD189 and this proposal. Bob noted that redirecting the user to
another section can cause confusion, but it might be the way to go in this case
to eliminate duplication. Bob noted one other difference. This proposal allows
corners for parameter values in order to align with the [Model] corner. BIRD189
interconnect models are not associated with a [Model]. Randy took an AR to make
a version of this draft that highlights text that is exactly the same as
BIRD189.
Randy reviewed the figure on page 8 that highlights all of the locations.
Arpad noted that the drawing only applies to a [Model] that doesn't use
[External Model]. Bob and Arpad questioned the purpose of the dotted line
triangle in the figure. Randy said he included it because it's a common symbol
for a buffer that's an output and an input. Randy said he was open to any
suggestions for clarifying the figure.
Bob and Arpad expressed some concerns about Buffer_I. Bob said it might be
confusing to some and indicate an Input buffer. Arpad said the "I" always makes
him think "current". At first, he suggested Buffer_In, and Randy was willing to
consider that. Randy noted that Buffer_I had been used for consistency with the
now removed Buffer_O. Arpad then reconsidered and thought Buffer_In might
itself
be misleading. He suggested Buffer_wfm, since it's just a location for the
waveform we will end up using for this C_comp model. However, Randy noted that
it would only be associated with the Input function. That's the only time you'd
be interested in measuring the input characteristics. No alternative proposal
supplanted Buffer_I.
Radek asked how the clamps participate in the simulation of the Input buffer
when you have the Buffer_I terminal. Randy referred to the following sentence
in Other Notes:
Note that [Power Clamp] and [GND Clamp] I-V table data, if present in a
[Model], is assumed to be applied at the Buffer I/O terminal and not at this
internal probing location.
Randy noted that all clamp tables from the [Model] are applied at the Buffer I/O
terminal.
- Mike L.: Motion to adjourn.
- Ambrish: Second.
- Arpad: Thank you all for joining.
AR: Randy to send out the modified draft, and Mike L. to post it to the ATM
archives.
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Next meeting: 12 March 2019 12:00pm PT
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IBIS Interconnect SPICE Wish List:
1) Simulator directives
