[ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
- From: Gregory R Edlund <gedlund@xxxxxxxxxx>
- To: Ambrish Varma <ambrishv@xxxxxxxxxxx>
- Date: Wed, 24 Aug 2011 10:26:17 -0500
Ambrish,
Thanks for your comments.
I was thinking along the same lines as you were: if the user is not aware
of what jitter terms are included inside the DLL and he or she assigns a
value to one of the jitter parameters, the simulator may produce excessive
jitter. So the IBIS committee needs to be clear about how we define each
jitter term and its association to a physical source. And the model
developer needs to tell the user what jitter terms are already included in
the DLL.
I'll draw up a block diagram and share it with the list. Maybe we can
agree on a common jitter model as we have agreed on a common flow.
Greg Edlund
Senior Engineer
Signal Integrity and System Timing
IBM Systems & Technology Group
3605 Hwy. 52 N Bldg 050-3
Rochester, MN 55901
From: Ambrish Varma <ambrishv@xxxxxxxxxxx>
To: Gregory R Edlund/Rochester/IBM@IBMUS
Cc: "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>,
"ibis-macro-bounce@xxxxxxxxxxxxx"
<ibis-macro-bounce@xxxxxxxxxxxxx>
Date: 08/24/2011 09:45 AM
Subject: RE: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Thanks for your response Greg,
My question was right after the ATM call – and there was a discussion of
how the Rx takes care of the jitter, what jitter does the model maker add
and how the EDA tool takes care of the rest – so the question might be a
little confusing – sorry about that.
I was following up on Fangyi’s remarks earlier – “Rx_Rj, Rx_Sj and Rx_DCD
are Rx model parameters. They are defined as impairments external to
receiver and serve the purpose of jitter budget analyses”.
When I was talking about budgets, I was referring to the jitter that the
EDA tool will inject to stress the Rx. This usually comes from the
specifications. So I was wondering if there is any chance of double
counting of the jitters if both the EDA tool and the model account for the
same jitter.
You suggestion of the block diagram makes a lot of sense and would help in
clearing the cloud over jitter analysis for AMI simulations.
Thanks,
Ambrish.
Ambrish Varma | Member of Consulting Staff
P: 978.262.6431 www.cadence.com
From: Gregory R Edlund [mailto:gedlund@xxxxxxxxxx]
Sent: Wednesday, August 24, 2011 9:00 AM
To: Ambrish Varma
Cc: ibis-macro@xxxxxxxxxxxxx; ibis-macro-bounce@xxxxxxxxxxxxx
Subject: Re: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Ambrish,
When you say "jitter budget," are you talking about something the
simulator keeps track of and reports to the user at the end of a
simulation? When I use the term "jitter budget," I usually mean
something outside of the simulator entirely, i.e. a benchmark for
comparison that I use to convince myself I believe the simulator.
The comments of Ambrish and others point out the need to have a clear
understanding of the Physical Sources of non-channel jitter, both
inside and outside the PHY. I would like to propose a block diagram,
similar to what Walter has done already in "Time Domain GetWave
Flow." If we hook up a TX circuit to an oscilloscope, we should see
the same jitter components that we see in simulation. I volunteer to
make the diagram with input of others on the list. Whatever solution
the committee arrives at for this BIRD needs to allow the simulator
to mimic the hardware.
Greg Edlund
Senior Engineer
Signal Integrity and System Timing
IBM Systems & Technology Group
3605 Hwy. 52 N Bldg 050-3
Rochester, MN 55901
Inactive hide details for Ambrish Varma ---08/23/2011 03:34:59
PM---Just wanted some understanding on how jitter budgets work:
Ambrish Varma ---08/23/2011 03:34:59 PM---Just wanted some
understanding on how jitter budgets work: Are the jitter inside the
tx and rx a par
From: Ambrish Varma <ambrishv@xxxxxxxxxxx>
To: "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
Date: 08/23/2011 03:34 PM
Subject: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Sent by: ibis-macro-bounce@xxxxxxxxxxxxx
Just wanted some understanding on how jitter budgets work: Are the
jitter inside the tx and rx a part of the budget – or are they
separate from the budget?
If they are a part of the entire budget for the simulation and the
ami file tells the EDA tool to add some Rx_Rj (for example) to the
Time domain simulation without the knowledge of the user (assuming
the user does not read the .ami file), wouldn’t the user be not
counting that jitter in the budget?
Thoughts?
Thanks,
-Ambrish.
Ambrish Varma | Member of Consulting Staff
P: 978.262.6431 www.cadence.com
From: ibis-macro-bounce@xxxxxxxxxxxxx [
mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of
fangyi_rao@xxxxxxxxxxx
Sent: Tuesday, August 23, 2011 2:48 PM
To: wkatz@xxxxxxxxxx; kumaran@xxxxxxxxxxxx;
vladimir_dmitriev-zdorov@xxxxxxxxxx; Arpad_Muranyi@xxxxxxxxxx;
ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
If they are external to Rx, user/EDA tool inject them into simulation
according to standard as simulation input instead of model
parameters. If they are internal to Rx, model makers don’t define
them.
So in both cases, we don’t need them as Rx model parameters.
Fangyi
From: Walter Katz [mailto:wkatz@xxxxxxxxxx]
Sent: Tuesday, August 23, 2011 11:42 AM
To: RAO,FANGYI (A-USA,ex1); kumaran@xxxxxxxxxxxx;
vladimir_dmitriev-zdorov@xxxxxxxxxx; Arpad_Muranyi@xxxxxxxxxx;
ibis-macro@xxxxxxxxxxxxx
Subject: RE: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Fangyi,
If the model maker did that, then he simply does not define Rx_Rj,
Rx_Sj and Rx_DCD.
Walter
From: fangyi_rao@xxxxxxxxxxx [mailto:fangyi_rao@xxxxxxxxxxx]
Sent: Tuesday, August 23, 2011 2:39 PM
To: wkatz@xxxxxxxxxx; kumaran@xxxxxxxxxxxx;
vladimir_dmitriev-zdorov@xxxxxxxxxx; Arpad_Muranyi@xxxxxxxxxx;
ibis-macro@xxxxxxxxxxxxx
Subject: RE: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Walter;
What I meant is when the Rx_Rj, Rx_Sj and Rx_DCD impairments are
internal to Tx, model maker can combine them into
Rx_Clock_Recovery_Rj, Rx_Clock_Recovery_Sj and Rx_Clock_Recovery_DCD
for statistical simulation, and include them in clock_times in
time-domain simulations.
Fangyi
From: Walter Katz [mailto:wkatz@xxxxxxxxxx]
Sent: Tuesday, August 23, 2011 11:31 AM
To: 'Kumaran Krishnasamy'; RAO,FANGYI (A-USA,ex1);
vladimir_dmitriev-zdorov@xxxxxxxxxx; Arpad_Muranyi@xxxxxxxxxx;
ibis-macro@xxxxxxxxxxxxx
Subject: RE: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Kumaran, Fangyi,
Comments below (WMK>).
Walter
From: Kumaran Krishnasamy [mailto:kumaran@xxxxxxxxxxxx]
Sent: Tuesday, August 23, 2011 1:39 PM
To: fangyi_rao@xxxxxxxxxxx; wkatz@xxxxxxxxxx;
vladimir_dmitriev-zdorov@xxxxxxxxxx; Arpad_Muranyi@xxxxxxxxxx;
ibis-macro@xxxxxxxxxxxxx
Subject: RE: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Hi,
To add to Fangyi’s first comment, users determine the amounts of
jitter from the standards (for example PCIe, SFI) that describe the
max amounts to be used to stress the Rx.
WMK> You are correct. In this case the User/EDA tool will specify
Rx_Rj, Rx_Sj and Rx_DCD from the particular standard.
Regards,
Kumaran
From: ibis-macro-bounce@xxxxxxxxxxxxx [
mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of
fangyi_rao@xxxxxxxxxxx
Sent: Tuesday, August 23, 2011 10:29 AM
To: wkatz@xxxxxxxxxx; vladimir_dmitriev-zdorov@xxxxxxxxxx;
Arpad_Muranyi@xxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Walter;
Thanks for the answers. Please see my further comment/question in
brown.
How would a model user know how to set Rx_Rj, Rx_Sj and Rx_DCD?
The BIRD states that they are external to the receiver, so it’s
expected that model users determine and inject (through simulator)
such jitters into simulations.
In some cases, for example a forwarded clock the User/EDA tool can
analyze the forwarded clock signal, in which case the EDA tool would
be directed to use these jitter impairments.
However, if the reference clock is generated inside the Rx chip, then
the model maker does know these jitter impairments, and can set them
inside the AMI model.
In that case they are not external to Rx. Can’t they be combined into
Rx_Clock_Recovery_Rj, Rx_Clock_Recovery_Sj and Rx_Clock_Recovery_DCD?
(Sj could be tricky but can be handled)
WMK> Are only Rx_Clock_Recovery_Rj, Rx_Clock_Recovery_Sj and
Rx_Clock_Recovery_DCD Are only used in statistical simulation (unless
the perverse case when Rx AMI_GetWave does not return clock_times).
Rx_Rj, Rx_Sj and Rx_DCD are used in both statistical and time domain
time domain simulations, so cannot be combined with
Rx_Clock_Recovery_Rj, Rx_Clock_Recovery_Sj and Rx_Clock_Recovery_DCD.
Fangyi
From: fangyi_rao@xxxxxxxxxxx [mailto:fangyi_rao@xxxxxxxxxxx]
Sent: Monday, August 22, 2011 9:02 PM
To: wkatz@xxxxxxxxxx; vladimir_dmitriev-zdorov@xxxxxxxxxx;
Arpad_Muranyi@xxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx
Subject: RE: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Hi, Walter;
I wonder why Rx_Rj, Rx_Sj and Rx_DCD are Rx model parameters. They
are defined as impairments external to receiver and serve the purpose
of jitter budget analyses. So they are simulation inputs but not
intrinsic Rx parameters. They should be set by model users instead of
model developers. EDA tools can include them in simulations by
allowing users to specify their values from the simulator.
Regards,
Fangyi
From: ibis-macro-bounce@xxxxxxxxxxxxx [
mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz
Sent: Wednesday, August 03, 2011 4:18 PM
To: 'Dmitriev-Zdorov, Vladimir'; 'Muranyi, Arpad'; 'IBIS-ATM'
Subject: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Vladimir,
We are planning to discuss the Jitter BIRD Tuesday. I think we can
resolve all of the questions at that time.
Walter
From: Dmitriev-Zdorov, Vladimir [
mailto:vladimir_dmitriev-zdorov@xxxxxxxxxx]
Sent: Wednesday, August 03, 2011 3:35 PM
To: wkatz@xxxxxxxxxx; Muranyi, Arpad; 'IBIS-ATM'
Subject: RE: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Walter,
After reading your comments, I’m more satisfied with the document.
Otherwise it’s hard to understand some things.
Still, I have a few remaining suggestions, shown in a few additional
comments.
Vladimir
From: ibis-macro-bounce@xxxxxxxxxxxxx [
mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz
Sent: Tuesday, August 02, 2011 5:00 PM
To: Muranyi, Arpad; 'IBIS-ATM'
Subject: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Arpad,
I am including my response to Vladimir’s comments in the enclosed
document. I stand by my earlier statement that I believe the current
specification defines each parameter mathematically precisely and
indicates how the parameters are to be used in either the statistical
or time domain simulations. I would not object to adding additional
words would be helpful to explain the precise mathematical
definitions with “C” code or other standard statistical function
definitions.
Walter
From: Muranyi, Arpad [mailto:Arpad_Muranyi@xxxxxxxxxx]
Sent: Tuesday, August 02, 2011 5:55 PM
To: Walter Katz; 'IBIS-ATM'
Subject: RE: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Walter,
Did you look at the comments Vladimir inserted in the
attached Word document? I think addressing those would
be a good start in this discussion. But there are some
specifics even in the body of the email from Vladimir:
“The Bird does not seem to be logically complete (does not cover all
cases, such as Time domain and Statistical flow), or does not provide
all necessary parameters affecting the results (such as either giving
frequency content of Tx Gaussian jitter, or making it defined as
white uncorrelated jitter, etc.) ”
Thanks,
Arpad
========================================================
From: Walter Katz [mailto:wkatz@xxxxxxxxxx]
Sent: Tuesday, August 02, 2011 4:45 PM
To: Muranyi, Arpad; 'IBIS-ATM'
Subject: RE: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Arpad, Vladimir,
There was great effort to define each of the parameters in strict
mathematical terms. Please indicate specific parameters that the BIRD
does not either define mathematically precisely, or indicate how the
parameters are to be used in either the statistical or time domain
simulations.
Walter
From: ibis-macro-bounce@xxxxxxxxxxxxx [
mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Tuesday, August 02, 2011 4:43 PM
To: IBIS-ATM
Subject: [ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
Walter,
Here is the email (with attachment) I mentioned in the
ATM meeting today. There was no response to it since
I posted it. I think it would be good to get some
discussion going on these questions/comments.
Thanks,
Arpad
From: ibis-macro-bounce@xxxxxxxxxxxxx [
mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Friday, July 01, 2011 11:53 AM
To: IBIS-ATM
Subject: [ibis-macro] Comments on BIRD 123.2.2 from Mentor
Walter and All,
I am forwarding Vladimir’s comments on BIRD 123.2.2 to this
list for discussion. Please look at his comments which are
in the attached Word document. Since Vladimir is also on
this email list, please direct your answers, questions and
comments to him. (I don’t want to be the middle man in such
conversations…).
The general problem is ambiguity of given definitions when it comes
to implementation in EDA tool.
The Bird does not seem to be logically complete (does not cover all
cases, such as Time domain and Statistical flow), or does not provide
all necessary parameters affecting the results (such as either giving
frequency content of Tx Gaussian jitter, or making it defined as
white uncorrelated jitter, etc.)
Thanks,
Arpad
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