Ed,
IBIS, prior to AMI modeling, was a language that described the IV and VT
characteristics of a buffer along with the method to derive these curves.
It has been enhanced to include timing measurements, and receiver and
driver waveform rules. AMI modeling added a different dimension to IBIS by
characterizing the equalization internal to Tx and Rx SerDes (and in the
near future single ended non SerDes buffers).
IBIS has gone out of its way to NOT describe an any Normative way the way
to use these models. There are AMI flows in the document, but I consider
these Informative.
The method that any specific EDA tool uses to generate the Impulse
Response of a channel, how an EDA tool sets up the inputs to AMI models,
and how an EDA tool evaluates the outputs of AMI models varies among EDA
tools. Each of the EDA vendors considers how they use AMI models in their
simulators proprietary.
As a user, you can be assured that each EDA tool will get the exact same
output of an AMI model if they give the AMI model that same input.
With respect to the PAM4 BIRD, what is lacking? The BIRD tells the EDA
tool how to generate an Impulse Response of a channel (exactly the same as
done for NRZ), and describes how to generate a PAM4 stimulus pattern for
the Tx. The Tx model maker needs to document the controls of the Tx that
are specific to the particular Tx. The PAM4 BIRD also describes how the Rx
tells the EDA tool the measurement levels that the EDA tool should use to
evaluate the equalized impulse response and waveforms that are generated
by the Rx model.
Walter
From: ibis-bounce@xxxxxxxxxxxxx [mailto:ibis-bounce@xxxxxxxxxxxxx] On
Behalf Of Ed Sayre
Sent: Tuesday, June 09, 2015 3:25 PM
To: bob@xxxxxxxxxxxxxxxxx; ibis@xxxxxxxxxxxxx
Subject: [ibis] Re: BIRD175.2: Extending IBIS-AMI for PAM4 Analysis
Bob:
A number of folks that I communicate with have expressed great frustration
with the use of IBIS-AMI models in their simulators of choice. Are there
examples and a user guide which go beyond the specification?
ed
From: ibis-bounce@xxxxxxxxxxxxx [mailto:ibis-bounce@xxxxxxxxxxxxx] On
Behalf Of Bob Ross
Sent: Tuesday, June 09, 2015 11:39 AM
To: ibis@xxxxxxxxxxxxx
Subject: [ibis] Re: BIRD175.2: Extending IBIS-AMI for PAM4 Analysis
All,
On re-reading BIRD175.2, I have a few comments:
1. Both "PAM4_UpperThreshold" and "PAM4_Upper_Threshold" appear in
BIRD175.2.
(Same for *Center_Threshold and *Lower_Threshold.)
I would prefer using the underbar "_" for these parameters and also for
the *Offset parameters.
2. For the *Threshold parameters, the rule:
. If the Reserved AMI Parameter Modulation is set to "PAM4" and
these threshold values are not declared, the model maker shall assume that
the EDA tool may choose a value for each of these three parameters.
should be changed.
All three parameters definitions should be declared if Modulation is set
to "PAM4" with Value
or in a List. Otherwise we are using "implicit" parameter definitions in
IBIS-AMI on unpredictable
results between EDA tools. However, the EDA tool can re-assign the
values.
3. The defaults of 0.0 are OK for the *Offset* parameters, if they are
missing.
(I will be out today, so I may not be able to respond.)
Bob
From: ibis-bounce@xxxxxxxxxxxxx [mailto:ibis-bounce@xxxxxxxxxxxxx] On
Behalf Of Mirmak, Michael
Sent: Friday, June 05, 2015 11:34 AM
To: ibis@xxxxxxxxxxxxx
Subject: [ibis] BIRD175.2: Extending IBIS-AMI for PAM4 Analysis
An updated BIRD175.2, Extending IBIS-AMI for PAM4 Analysis, has been
submitted on behalf of Walter Katz, Mike Steinberger, and Todd Westerhoff
of SiSoft; Fangyi Rao of Keysight Technologies; Bob Miller of Avago
Technologies; and Hongtao Zhang of Xilinx. It will be discussed at the
next IBIS Open Forum teleconference.
The text of the BIRD can be viewed at
http://www.eda.org/ibis/birds/bird175.2.docx.
Michael Mirmak
Intel Corp.
Chair, IBIS Open Forum
http://www.eda.org/ibis/
