XAUI Jitter Protocol 4th April 2001
XAUI Jitter Protocol
4th April 2001
Chair :
Anthony Sanders@xxxxxxxxxxxx
Attendants :
Michael Debie <MDebie@xxxxxxxxxxxxxxxxx>,
Jeff Porter <j.porter@xxxxxxxxxxxx>,
jmw(Mike) <jmw@xxxxxxxxxxx>
Tord Haulin <tord.haulin@xxxxxxxxxxxxx>,
Tom Lindsay <Tom.Lindsay@xxxxxxxxx>
(D) - previous email comment from Dawson
(T) - previous email comment from Tom
As Dawson will not be with us today, would like to concerntrate on the points that are purely jitter related.
(D) The draft standard was unanimously approved for 802.3 Working Group ballot. This indicates that the attendees believed the draft is "technically complete", meaning that further technical refinements are anticipated but there are no known technical holes or insurmountable barriers. W.G. ballot is scheduled to begin on April 6 and end May 11.
1.2 Very Low Frequency Jitter Definition Frequency And Amplitude
The sinuosoidal jitter that is currently defined for Jitter Tolerance, is capable of generating phase offset between channels that are greater than the demultiplexed 10b word boundary. This test however, is implementation and shall not be discussed anymore in this adhoc.
2.5.1 Annex 48b
(D) The XAUI jitter methodology was discussed in detail and given a vote of confidence. Annex 48B was approved describing this methodology. (Presentation or clarifications needed.)
The adhoc is of the opinion that due to the complexity of jitter and the current implications of the jitter methodology that is being defined, a Tutorial on jitter at the next available date would be advantageous in eduating both the commitee and help bring the current proposals to final specification. Michael Debie from Wavecrest volunteed equipment that could be made available for also demonstrated the methods described.
A- Arrange tutorial (Ant)
Main next steps for Annex 48B is to clarify and remove any inconsistencies. This may require the removal of the reference to MJS and insertion of the necessary text directly in the text. This shall be further seen over the next week as the Annex is updates by myself.
(T) For tolerance testing, add sine jitter after calibration of DJ, TJ, and amplitude. Calibration should be based on the minimum quality OUTPUT signals defined at the end of the channel. Then, since sine jitter truly represents margin for unknown external effects in real systems, then both jitter and amplitude can be degraded to worse than those minimum output signals.
A- This should be added to 48B.2 under calibration
The following is the current defintion for the calibration of the receiver signal for jitter tolerance testing.
- Set 200ppm Offset Between Transmit And Receive Clock
- Enable All Channels In Transmit And Receive Direction
- Using Cjpat
- Transmitter + Dj + Rj -> Channel -> Rx Data Eye
- Calibrate Dj And Rj Of Rx Data Eye To Confirm To Specified
Receive Jitter
- Adjust Output Level Of Pattern Generator Such That Eye
Amplitude = Channel Rx Eye
- Verify Rx Data Eye Vs. Receive Data Eye Mask Without Sj
- Add Specified Sj For Given Frequency
- Verify Rx Data Eye Vs. Receive Data Eye Mask With Sj
- Verify Ber Of Reciever
(T) Did we include a method for deconvolving DJ from TJ? Annex A.3 in FC-PI has a 2-point method outlined, but it needs correction (I wrote that section, so I know what I screwed up). Some method for
deconvolution is probably a good idea. It does not exist cleanly anywhere in MJS.
A- Tom to send out explanatory email concerning this curve fitting point.
(T) I sent an email out recently that dealt with potential issues between jitter specs and clock frequency specs. I have to confess I haven't had time to complete my thoughts on this, but I sense there
are some holes between these 2 specs that could cause problems, at least in concept. I'll try to continue work on this if/when I ever find the time.
A- Tom to think about whether he wants to send something out.
2.5.2 Clause 47
A- Final update of Clause 47 needed (see attachment below). All adhoc members should read through proposals and be prepared to make comments.
A- Make sure that Golden PLL, is not referenced, only HPF. (Allows for TIA).
A- Includes reference in methodology conerning clock offsets and asynchronous clocks for transmit and receive paths.
A- We need a note concerning where the data eye mask is position in the data eye!!!!!
(T) Need horizontal (time) definitions for 0 and 1 UI for mask positioning. Presently, the mask is centered, yet 0 and 1 are not defined. I propose that 0 and 1 be defined by the mean of the crossing
histograms. Most CDRs probably use media, which is very similar to mean in most cases and is quick and consistent. Beyond this, there may be some that would like the mask to NOT be centered. I am okay with
this, if it makes sense - it would imply an asymmetrical mask. However, I am against the ability to float the mask around as needed to clear the signal traces...
A- This should be added to data eye part of specification, or as clarification in Annex48B
- The mean as opposed to the median should be the easiest method.
4.4 Fext/Next (Cross Talk)
A- Theoritical Simulation Of Expected Differential Crosstalk To Be
Done (Anthony)
Basically have seen that crosstalk on PCB and package is nothing.... <-60dB.
4.7 Group Delay Of Channel
A- Comment To Be Entered That Group Delay Definition To Be Removed
And A Minimum Dj Should Be Defined That Must Be Induced By The
Channel, For A Given Pattern, And Transmit Waveform.
(D) The compliance channel group delay spec appears "broken". There is
some work in progress toward a solution. (Note 1)
This shall be discussed in next telco.
6.4 Defined Patterns
A- Final Acceptance Of Proposed Pattern.
No new input from 10G Pattern discussion.
This point should be closed now.
6.4.1 Compliance Definition
A- Additional 0.05UI of jitter must be found from somewhere. This is to be discussed in this telco.
A- Must we add the DJ really together...??? We must somehow decide whether all this jitter is data dependant and correlated or not. This would allow us to use convolution, which may give as a few mUI here and there.
A- Tom to repost information concerning effect of random jitter on effective DJ.
A- Proposal to solve the current jitter specification.
- Increase channel jitter to 0.2UI
- "Other" should be treated as SJ depending upon whether we are talking about compliance testing or system budget.
- Make "Other" 0.1UI for system budget to avoid confusion.
10. Overall Verification Of Jitter Budget
A- Ongoing Simulations For Verification Of Newly Proposed Jitter
Numbers And Patterns Are Ongoing By
Closed.
A- Convertion of the SJ jitter from Giga into absolute time offset
must be done (Ant)
Ongoing,... have models runnning at the moment, and hope to have results
in the coming week.
11. XAUI Signal Detect
(D) The XAUI signal detect issue was unanimously resolved: There is no
additional signal_detect pin or mandatory loss-of-signal detection on
the XAUI. This was the only change to clause 47 in going from D2.2 to
D2.3. (The D2.3 draft now available to task force members on the web
site.)
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Section 47 Attachment
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47.4.1 Jitter test requirements
Terms and definitions for effective jitter and random error processes
as used by this specification are defined in Annex.48B.1 and should be
studied carefully before compliance testing is started.
47.4.1.x Transmit Output Jitter
47.4.1.x.x Transmitter With No Implemented Equalization.
The output of the driver when terminated as defined in section
47.3.3 and measured using one of the reference methods as defined in
Annex.48B.3 shall conform to
a) the specified transmitter deterministic and random jitter as
defined in table 47-2, and
b) the data eye as defined in figure 47.7 and table 47.4.
under the conditions that
a) the transmission pattern is CJPAT, as defined in Annex.48A,
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b) the extracted clock used for measurement is High Pass Filtered
with a corner frequency of 3.125GHz / 1667 and 20dB rolloff, based
on the theory presented in of Annex 48B.1.5, and
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c) all other channels in the transmit and receive direction are
active.
47.4.1.x.x Transmitter With Implemented Equalisation
Using one of the reference methods as defined in Annex.48B.3 both
a) the output of the driver when terminated as defined in section
47.3.3 and
b) the output of the filtered driver where the filter has a worst
reponse than defined for the compliance channel, section
47.3.3.5. and is terminated, as defined in section 47.3.3
shall conform to
a) the specified receiver deterministic and random
jitter as defined in table 47.5, and
b) the data eye as defined in figure 47.4 and table 47.3 (without
sinusoidal jitter)
under the conditions that
a) the transmission pattern is CJPAT
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b) the extracted clock used for measurement is High Pass Filtered
with a corner frequency of 3.125GHz / 1667 and 20dB rolloff, based
on the theory presented in of Annex 48B.1.5, and
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c) all other channels in the transmit and receive direction are
active and terminated with valid data. (Clocks are not synchronised.)
47.4.1.x Receiver Tolerance Testing
Using one the reference methods defined in Annex.48B.2 the receiver
shall tolerate the specified deterministic and random jitter as
defined in table 47.5 given the additionally applied sinusoidal
jitter mask, section 47.3.4.4., for all frequencies, under the
conditions that
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a) a stressed signal with data eye opening amplitude equal to
receiver sensitivity, defined in 47-4, but conforming to the data
eye defined in 47.4, generated given the reference method defined in
Annex 48.B.4. is used
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b) all other channels in the transmit and receive direction are
active. Include clock offset
c) the received pattern is CJPAT
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