[ibis-macro] Re: Comments on BIRD 123.2.2 from Mentor
- From: Ambrish Varma <ambrishv@xxxxxxxxxxx>
- To: Gregory R Edlund <gedlund@xxxxxxxxxx>
- Date: Wed, 24 Aug 2011 07:44:04 -0700
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.
[cid:image003.gif@01CC624A.599A7B20]
Ambrish Varma | Member of Consulting Staff
P: 978.262.6431 www.cadence.com<http://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
[cid:image001.gif@01CC624A.599A7B20]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.
[cid:image003.gif@01CC624A.599A7B20]
Ambrish Varma | Member of Consulting Staff
P: 978.262.6431 www.cadence.com<http://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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