Minutes from the 30 Jul 2019 IBIS ATM Task Group meeting are attached.
Mike
IBIS Macromodel Task Group
Meeting date: 30 July 2019
Members (asterisk for those attending):
ANSYS: Dan Dvorscak
Curtis Clark
Cadence Design Systems: Ambrish Varma
Ken Willis
Intel: * Michael Mirmak
Keysight Technologies: * Fangyi Rao
Radek Biernacki
Ming Yan
Stephen Slater
Maziar Farahmand
Mentor, A Siemens Business: * Arpad Muranyi
Micron Technology: Randy Wolff
Justin Butterfield
SiSoft (Mathworks): * Walter Katz
* Mike LaBonte
SPISim: * Wei-hsing Huang
Teraspeed Labs: * Bob Ross
The meeting was led by Arpad Muranyi. Mike LaBonte took the minutes.
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Opens:
- None
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Review of ARs:
- Fangyi to create BIRD197.4 incorporating changes from his new BIRD and
comments.
- Done
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Call for patent disclosure:
- None.
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Review of Meeting Minutes:
Arpad asked for any comments or corrections to the minutes of the July 23
meeting.
Mike LaBonte noted that the minutes incorrectly gave the meeting date as July
16.
Michael Mirmak moved to approve the minutes. Bob Ross seconded the motion.
There were
no objections.
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New Discussion:
Jitter HF/LF components BIRD draft:
Michael Mirmak showed a draft BIRD "Separating High and Low Frequency Tx Random
Jitter
Parameters". Michael said channel amplification of jitter applied more to
higher
frequencies than lower frequencies. The BIRD would split jitter into high and
low freq
bins. The user would not have to re-budget jitter, moving some jitter to the
Rx side.
Tx_Rx would not be deprecated, and it would be synonymous with Tx_Rj_HF.
Tx_Rj_LF would
be new. The new parameters would not be legal before version 7.1. The cutoff
frequency
would not be specified, that left to the model maker. There had been
suggestions of
a jitter distribution function, but Michael felt that was not yet needed.
Arpad Muranyi asked if Tx_Rj_HF would be required if Tx_Rj_LF was present.
Michael said
it should be, and it would be OK to have a rule that if Tx_Rj were present the
others
were not allowed. Arpad said we had been trying to avoid parameters with
double meaning,
preferring mutually exclusive use. Walter Katz likened the proposal to
Rx_Noise and
Rx_Gaussian_Noise, an "alias". He suggested having it that way for Tx_Rj and
Tx_Rj_HF,
keeping them synonymous. Michael suggested that the presence of Tx_Rj_LF would
then
require Tx_Rj or Tx_Rj_HF.
Walter Katz asked if Tx_Rj_HF would adjust the stimulus going into the Rx.
Michael
Mirmak said they had statistical analysis in mind, and he needed to check with
experts
on their preference for bit by bit mode. In statistical mode a distinction
between LF
and HF required users to edit the Rx jitter to include Tx LF jitter. Walter
asked if
there was no Rx_Rj, and the Tx had Tx_Rj_LF, would the EDA tool act as if the
Rx had
that LF jitter? Michael said it would.
Walter gave an example of how an EDA tool might handle jitter data, with
picosecond
values. Michael noted that the BIRD avoided specifying the exact math. Walter
felt it
would be helpful for EDA tools to have more detail on the requirement. Arpad
agreed.
Fangyi suggested giving an example of one way to do it, allowing tools to
innovate.
Another method would be to say it is statistically uncorrelated. Arpad noted
that a
CDR tracking out low frequency jitter might negate that component. Michael
said that
sounded like we would effectively be providing Tx_Rj_HF only. The allocation
of the
LF/HF would matter. He will ask others about that. Arpad said there could be
limits
to the ability of a CDR to follow the LF jitter. Michael suggested we might
specify a
frequency dependent sensitivity threshold.
Fangyi asked if the Tx vendor would need to know how the Rx functions. Michael
Mirmak
said the Tx should not need to know details of the Rx, but certain assumptions
would
be needed. Walter Katz noted that Sj is similar, and generally it is an LF
component.
The shapes are different; Sj has no tail on the distribution curve. Had Sj
been tried as
an alternative means of representing LF jitter? Michael said he was working on
getting
that answer. His understanding was that Sj constituted a single tone. Walter
said
it amounted to a dual Dirac function at the Rx. The question was whether or not
it
was bounded. Sj was usually due to power supply noise, which usually is
bounded.
Standards for jitter specified tests that can be implemented by scopes, and
standard
distributions are usually applied. Arpad Muranyi said they measure frequency
modulation
and DCD, analyzing whether they were moving and with respect to what.
Mike LaBonte asked if Tx modelers had to consider only the channel, or the Rx
too.
Michael Mirmak felt we might need to specify a distribution, not an unspecified
cutoff
point. The Tx should not have to know exactly what the Rx is. Arpad asked why
the
cutoff need not be known. Michael said the cutoff point should not make much
difference.
The idea was hat it would be unlikely for someone to connect Ethernet and PCIe
devices
together for example, so it was simpler to just say one bucket of jitter is
affected
by the channel and another bucket isn't. If the Rx must be considered, a
distribution
curve might be better. Fangyi asked if statistical analysis would not model
the CDR,
and be more affected by the jitter. Michael Mirmak said that could not be
assumed,
impacts on clock recovery could be modeled statistically.
Digital signatures:
Michael Mirmak said digitally signing DLLS was a good practice, but not
something
to be specified by IBIS. For security, users should be able to verify the
source of
a DLL. Arpad Muranyi said one question was who would be the gatekeeper. Would
IBIS
issue the signatures? Mike LaBonte said that as an unincorporated
organization, the
IBIS Open Forum might not have standing to procure a signing certificate.
Also, IBIS
would then become the issuer guaranteeing the origin of the models, It would be
best
for model suppliers to sign the models. Wei Hsing Huang described the
certification
process, which involves business verification. Walter suggested we could
describe
the steps for model makers to handle the digital signatures, to help them get
started.
Wei Hsing said web browsers had the ability do the checking when models were
downloaded.
Arpad asked if this should remain on the agenda. Michael said it could be
removed
from the agenda, but the topic would make a great summit presentation.
PAM4 threshold consistency:
Arpad Muranyi showed IBIS 7.0 page 255. He asked if we required associated PAM4
thresholds to all have the same Usage. He noted that Out and Info were both
used in two
examples, but the Usage was consistent within each example. Yet, this was not
specified.
Walter Katz suggested the PAM4_Upper_Threshold and PAM4_Lower_Threshold could
be Out,
for example, and the center could be Info because it would always be assumed to
be zero.
Arpad asked if a BIRD should be written. Walter suggested no BIRD was needed.
Walter Katz moved to adjourn. Michael Mirmak seconded. Without objection the
meeting adjourned.
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Next meeting: 06 August 2019 12:00pm PT
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IBIS Interconnect SPICE Wish List:
1) Simulator directives
