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IBIS INTERCONNECT TASK GROUP
http://www.ibis.org/interconnect_wip/
Mailing list: ibis-interconnect@freelists.org
Archives at http://www.freelists.org/archive/ibis-interconn/
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Attendees from April 11, 2018 Meeting (* means attended at least using audio)
ANSYS Curtis Clark
Cadence Design Systems Bradley Brim
Intel Corp. Michael Mirmak*
Keysight Technologies Radek Biernacki
Mentor, A Siemens Business Arpad Muranyi*
Micron Technology Justin Butterfield*, Randy Wolff*
SiSoft Walter Katz*, Mike LaBonte*
Teraspeed Labs Bob Ross*
Michael Mirmak convened the meeting. No patents were declared.
Justin Butterfield took minutes.
Review of Minutes:
- Michael called for review of the minutes from the April 6 meeting. Bob Ross
noted that he intend "node 0" to be the preferred quoted text in BIRD189
rather than node "0" as stated in the minutes. Bob moved to approve the
minutes with this correction. Mike LaBonte seconded. The minutes were
approved without objection.
Review of ARs:
- Arpad Muranyi to review the "Important" paragraphs on page 30 for inclusion in
BIRD189.
- Michael noted that this is done.
- Walter Katz to write up some text on the two types of models.
- Walter reported he sent this out, but he is in the process of revising it.
And, he would like to discuss the text today.
- Radek to improve the language of the first and second "Important" notes on
page 30.
- Michael noted that this was sent out.
Opens:
- None
BIRD189.5_draft18_v7 Review:
Walter reviewed the text he sent out over email. He suggested that models which
use node 0 inside an IBIS-ISS subcircuit are not suitable for power aware
simulations. Michael asked if Radek was proposing a parser message for having
node 0 at the ATM meeting, and if there was any opposition to this. Arpad
stated that it was not agreed upon to add a parser message, but the EDA tool
could do it. Bob commented that he does not want the parser to dig into the
IBIS-ISS file. Walter stated he agreed and we should not do a message at all.
Walter noted the historical usage of ground is implemented as node 0. Some
power aware simulations need to account for the return path currents. The
reference node needs to be physically close at 1/10 of a UI wavelength or less.
His intent is to bring up the fundamental issues of accounting for the return
current and the reference node.
Michael asked how we would put this text in BIRD189. Walter thought it should
go in the beginning of the IBIS specification or in a supporting document. Bob
agreed with putting the text in a supporting document, and he noted that this is
talking about physical measurements and simulations. But, we may need some fine
tuning of the text to clarify. Arpad noted in simulations we can do all
measurements in reference to the global ground, but physical measurements must
be done with the reference close. He also suggested to change the first bullet
to past tense.
Randy Wolff asked if this text will be in BIRD189 and if discussion can be
deferred. Arpad stated that Walter wanted it in the beginning of the IBIS
specification. Michael noted it could be part of another BIRD.
Arpad asked how this statement is going to help us. Walter thought that this
could replace Radek's warning with a more general statement. Michael stated
that the issue is if you have models with different assumptions for
referencing, this could give the user wrong results. He asked if we should take
the approach to educate the model maker or to warn the user they may get
incorrect results.
Michael asked Arpad if there were any changes to his Important note text. Arpad
replied that there were no changes after our last meeting.
Michael shared Radek's new Warning text that was sent out. Bob stated he has
some questions about the text. A minor change he suggested was to change
incorrect to less accurate. Also, he is assuming that an A_gnd pin exists at
the pin interface. Michael commented that there is a terminal that will be the
reference.
Arpad asked about the phrase "shall be treated as", and if it means we should be
bring out the node 0 as a terminal or if the simulator acts like this node is
there. Arpad commented that a global node is a shortcut that you do not need to
connected at each level of the subcircuit hierarchy. Michael noted the options
for handling node 0 are to force the model maker to explicitly change the model,
add an additional terminal when the user netlists, or the math behind the scenes
changes. Arpad asked if this is a warning saying that the math is not
changing. Michael noted that the math may not be consistent. Bob thought it
could be less accurate or the effects could be negligible.
Arpad asked if we could envision a situation where node 0 should not be brought
out intentionally. He wondered how we would know when to connect node 0 and
when to not. Michael stated the problem is when we mix the models with
different references. He asked if we should change the text to reflect the
mixed reference case. Arpad noted that the mixed cases might still work okay.
Michael stated that this might be true, but it depends on the case. He sees
simulation issues with mixing references and inadvertent use of node 0
frequently.
Michael asked if changing the phrase "shall be treated as" would resolve the
issue. Bob noted there are some other changes he would like. Mike asked if
the second clause is backwards. The other question is if this text is asking
the netlister to do something different based whether node 0 is found. Arpad
asked if this is a warning to the user or if this is a statement to the EDA
tool. Randy commented that this is saying that the tool should not leave node
0 floating. Michael will ask Radek if this is a tool instruction and if we can
change the phrase "shall be treated as" [AR].
Michael asked if this will resolve the three comments in the BIRD. Bob thought
yes, but there are still details to discuss.
Michael asked if we have a resolution on the rail rule relaxation. Arpad asked
if we can remove the text associated with this, as he does not want to delay
BIRD189 further. Bob stated that he would like to discuss these changes.
Unlike the IO terminals there is not an assumed connection for rails. He
stated he was asked by this committee to put these changes in. Arpad said the
text could be separated. Bob would like to discuss it before voting on the
BIRD in the Open Forum. Michael suggested that we discuss the rail rules in
the next meeting. Bob agreed.
Next Meeting:
The next meeting will be April 18.
Mike moved to adjourn. Bob seconded. The meeting adjourned without
objection.
Task List
BIRD189.5 editorial additions/changes to be completed:
1. Resolve inconsistency with using node 0 and node "0" by replacing with
"node 0".