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RE: [802.3ae_Serial] RE: CRPAT / CJPAT Pattern Question



CJPAT has both disparities built into each repetition. This was done
knowing that disparity could not be controlled, but half of the pattern
would have the desired properties. Can't predict which half, but that
does not matter. CJPAT is okay.
 
This is not true for CRPAT. It was clearly designed for only negative
running disparity at its start. This is one of my comments.
 
Tom

	-----Original Message----- 
	From: THALER,PAT (A-Roseville,ex1) 
	Sent: Mon 6/25/2001 2:26 PM 
	To: Lindsay, Tom; DAmbrosia, John F; Mike Jenkins 
	Cc: stds-802-3-hssg-serialpmd@ieee.org 
	Subject: [802.3ae_Serial] RE: CRPAT / CJPAT Pattern Question
	
	


	I think someone also needs to verify that both disparities of
the patterns 
	provide the desired spectral characateristics since we do not
control 
	disparity and the disparity flipped pattern is a different
pattern than the 
	original CJPAT. 
	  
	Pat 
	  
	  
	-----Original Message----- 
	From: Lindsay, Tom [ mailto:tlindsay@stratoslightwave.com] 
	Sent: Saturday, June 23, 2001 3:58 PM 
	To: DAmbrosia, John F; Mike Jenkins 
	Cc: stds-802-3-hssg-serialpmd@ieee.org 
	Subject: RE: CRPAT / CJPAT Pattern Question 


	This thread never really completed, so here is the suggested
remedy I am 
	submitting with my letter ballot: 

	Time-stagger the payload portion of the patterns in the lanes. I
propose the 
	staggering for CJPAT be such that lanes 0 & 2 remain as they
are, but lanes 
	1 & 3 rotate 140 bytes each. This will retain the special
properties of this 
	pattern within each lane. 
	  
	I suggest CRPAT be rotated 3 bytes (~90 degrees per repetition)
per lane, 
	although I have another comment that suggests CRPAT has other
potentially 
	serious issues, and this change may cause worse problems. 

	
	I THINK this addresses the thread, but I expect others will
correct me as 
	appropriate. The suggested remedy does NOT invert the data (this
is not 
	possible with 8B10B), but does attempt to provide a compromised
"mixing" of 
	edges and frequencies. 
	  
	***** 
	  
	The "other" comment about CRPAT is 
	CRPAT may not meet its objectives of randomness unless disparity
is 
	controlled (on each lane) as is done in Fibre Channel. However,
this may not 
	be important, since this pattern is not referenced by other
sections of the 
	standard. 
	  
	The suggested remedy is 
	Option A: Delete section 48A.4. 
	Option B: Build up the pattern like CJPAT is where both
disparities of the 
	pattern will exist, assuring that one is always correct. This
would take a 
	few hours of effort. 
	Option C: Convince me that disparity is controlled such that the
payload 
	portion starts positive. 
	Option D: Add a statement "The intended spectral density of this
pattern may 
	not be achieved unless the ending running disparity of
START/PREAMBLE/SFD is 
	controlled to be positive. 
	If option B, C, or D is chosen, then also add a note explaining
that "this 
	pattern is not intended for compliance testing, but it may
useful for 
	unspecified diagnostic purposes." 

	***** 
	  
	Tom Lindsay 
	Stratos 


	-----Original Message----- 
	From: DAmbrosia, John F 
	Sent: Fri 6/15/2001 9:51 AM 
	To: Lindsay, Tom; Mike Jenkins 
	Cc: stds-802-3-hssg-serialpmd@ieee.org 
	Subject: RE: CRPAT / CJPAT Pattern Question 



	Tom, 
	Slipping by any number of bits would be preferrable. 
	i am thinking about any type of testing that would use the CJPAT
or CRPAT. 
	You could have this type of phenomenon happen on board level
testing. 

	John 

	-----Original Message----- 
	From: Lindsay, Tom [ mailto:tlindsay@stratoslightwave.com 
	< mailto:tlindsay@stratoslightwave.com> ] 
	Sent: Friday, June 15, 2001 12:21 PM 
	To: DAmbrosia, John F; Mike Jenkins 
	Cc: stds-802-3-hssg-serialpmd@ieee.org 
	Subject: RE: CRPAT / CJPAT Pattern Question 


	John - 

	I just sent a note before I saw this. 

	Given the restrictions of 8B10B, slipping the pattern by a bit
is not 
	possible. It could easily be slipped by as little as 1 byte (10
bits), 
	but without disparity control, you may still not get the same
serial 
	pattern. 

	A basic question - are you thinking of a board level test or a
system 
	compliance test? 

	Tom 

	-----Original Message----- 
	From: DAmbrosia, John F [
mailto:john.dambrosia@tycoelectronics.com 
	< mailto:john.dambrosia@tycoelectronics.com> ] 
	Sent: Friday, June 15, 2001 8:35 AM 
	To: 'Mike Jenkins' 
	Cc: stds-802-3-hssg-serialpmd@ieee.org 
	Subject: RE: CRPAT / CJPAT Pattern Question 



	Everyone, 
	THere are multiple issues here, so let me try to go through it
again.  I 
	think we may be at a point where it is really an "implication "
thing 
	that 
	we can only try to inform about. 

	I would like to refer everyone to the presentation that was
given in St. 
	Louis - 

	
http://grouper.ieee.org/groups/802/3/ae/public/may01/dambrosia_2_0501.pd
<
http://grouper.ieee.org/groups/802/3/ae/public/may01/dambrosia_2_0501.pd
> 
	f 

	There are two aspects to the crosstalk analysis.  The first part
looked 
	at 
	the noise values (both near and far-end)created in the HM-Zd
connector. 
	During this analysis worst-case switching patterns, intended to
maximize 
	the 
	amount of crosstalk, were used.  You can see, how the worst case
switching 
	would be dependent on the connector pinout. 

	In the second part of the presentation, we ran a system
simulation of 
	the 
	XAUI channel.  We used one pinout and either switched signals in
phase 
	or 
	out of phase with the signal under consideration.  When adjacent
signals 
	are 
	switched in-phase, the overall performance of the system was
better than 
	when no adjacent signals were switched or when they were
switched out of 
	phase. In our simulation we assumed a bottom layer connection
(i.e. 
	traces 
	go through the via to the bottom layer).  When assuming a top
layer 
	connection, this affect is even more dramatic. 

	So it was my concern that crosstalk between the 4 lanes in a
single 
	channel 
	would result in  artifically improved performance, which would
improve 
	overall measured performance in a system environment where other
crosstalk 
	sources are then be factored in. 

	Perhaps another suggestion is to use the same data pattern for
each 
	lane, 
	but delay each by a bit?  We can leverage off of CRPAT and
CJPAT, which 
	were 
	intended to test jitter, and include potential crosstalk
effects.  I 
	don't 
	think a PRBS pattern will stress the jitter performance, since
this is 
	what 
	CJPAT is intended to do, right? 

	John 

	-----Original Message----- 
	From: Mike Jenkins [ mailto:jenkins@lsil.com <
mailto:jenkins@lsil.com> ] 
	Sent: Thursday, June 14, 2001 10:19 PM 
	Cc: stds-802-3-hssg-serialpmd@ieee.org 
	Subject: Re: CRPAT / CJPAT Pattern Question 



	All, 

	I want to step back a second to point out what this conversation
is aimed at.  Changing the pattern on three lanes to see the effect 
	at the receiver of the 4th lane is manipulating far-end
crosstalk 
	(FEXT).  FEXT is much smaller than near-end crosstalk (NEXT)
because 
	the inductive and capacitive components subtract in FEXT but add
in NEXT.  The NEXT for a receiver is created by the transmitters 
	in the same device as the receiver under test.  If these
transmitters 
	are sending CRPAT (or whatever) asynchronously, all possible 
	combinations will occur to close the receiver eye.
Extraordinary 
	efforts to manipulate FEXT are probably for relatively rather
small 
	returns in additional eye closure. 

	Regards, 
	Mike 

	pat_thaler@agilent.com wrote: 
	> 
	> Michael, 
	> 
	> >From my experience testing crosstalk,  single frequency
stimulus 
	signals 
	> would not be an effective way of testing crosstalk. Generally,
the 
	received 
	> crosstalk from a disturber such as an adjacent signal path is
the sum 
	of 
	> many crosstalk components each coupling in with its own phase.
Because 
	of 
	> this, the crosstalk is not a smooth function with frequency.
It 
	bounces 
	> around staying under an envelope where the envelope is the
amplitude 
	you 
	get 
	> when all the components add in phase. Therefore, testing
crosstalk at 
	a 
	few 
	> discrete frequencies doesn't tell you much about where the
envelope 
	lies. 
	> 
	> Generally one wants to test crosstalk with a signal containing
a broad 
	> spectrum of frequencies (e.g. CRPAT or even the normal idle
signal 
	since 
	we 
	> designed that to spread energy across the spectrum). One of
the 
	reasons 
	put 
	> forth in favor of having individual lane disables was that one
could 
	test 
	> crosstalk from one lane by disabling the other transmitters. 
	Therefore, we 
	> don't need to do any special patterns for crosstalk
measurement. 
	> 
	> Pat 
	> 
	> -----Original Message----- 
	> From: Michael Debie [ mailto:mdebie@wavecrest.com 
	< mailto:mdebie@wavecrest.com> ] 
	> Sent: Thursday, June 14, 2001 9:47 AM 
	> To: 'DAmbrosia, John F'; Michael Debie; 'Serial PMD reflector 
	(E-mail)' 
	> Subject: RE: CRPAT / CJPAT Pattern Question 
	> 
	> John, 
	> 
	> Absolutely agree.  I was just simplifying my description to
one lane, 
	but, 
	I 
	> assumed we would test each lane individually.  As far as the
pattern 
	> selection is concerned, the use of different patterns on each
lane 
	allows 
	us 
	> to see the contribution each of the other lanes has on cross
talk 
	noise. 
	> For example, suppose Lane 1 was driving a /5 clock like
pattern 
	(1111100000) 
	> the FFT of the jitter on the Lane under test would show a
spectral 
	line at 
	> Fc/10 and the amplitude of the spectral line would be the
pk-pk impact 
	on 
	DJ 
	> that Lane 1 has on the Lane Under Test (LUT?). We could set up
the 
	other 3 
	> lanes with varying degrees of clock like patterns and quickly
estimate 
	each 
	> lanes contribution to crosstalk on the LUT.  We could perform
this 
	test on 
	> all 4 lanes to measure crosstalk contribution.  It would also
be 
	interesting 
	> to sweep through several clock like frequencies on the non
tested 
	lanes to 
	> quantify the impact of crosstalk as a function of
instantaneous 
	frequency. 
	> The test in which we apply the same pattern on all of the non
tested 
	lanes 
	> will tell us how the crosstalk components combine. 
	> 
	> Regards, 
	> Michael 
	> -----Original Message----- 
	> From: DAmbrosia, John F [
mailto:john.dambrosia@tycoelectronics.com 
	< mailto:john.dambrosia@tycoelectronics.com> ] 
	> Sent: Thursday, June 14, 2001 9:11 AM 
	> To: 'Michael Debie'; 'Serial PMD reflector (E-mail)' 
	> Subject: RE: CRPAT / CJPAT Pattern Question 
	> 
	> Michael, 
	> I think your second proposal makes more sense, but i think it
would 
	need 
	to 
	> go one step further.  I think we should cycle which lane is
the 
	"different" 
	> lane like this- 
	> 
	>                 Pat 1A  Pat 1B  Pat 1C  Pat 1D 
	> Lane A  +               -               -               - 
	> Lane B  -               +               -               - 
	> Lane C  -               -               +               - 
	> Lane D  -               -               -               + 
	> 
	> Where the "+" lane would be the pattern, and the "-" would be
the 
	> compliment.  Thus, all channels get examined.  If only 1 lane
is 
	tested, 
	> then the test is specific to the implemenation, where if all
lanes in 
	a 
	> channel get examined, then the performance of the channel is
fully 
	examined 
	> rather than 1/4 of it. 
	> 
	> John 
	> 
	> -----Original Message----- 
	> From: Michael Debie [ mailto:mdebie@wavecrest.com 
	< mailto:mdebie@wavecrest.com> ] 
	> Sent: Wednesday, June 13, 2001 5:41 PM 
	> To: DAmbrosia, John F 
	> Subject: RE: CRPAT / CJPAT Pattern Question 
	> 
	> John, 
	> 
	> A good diagnostic for cross talk would be to place different
frequency 
	clock 
	> like patterns on all of the lanes.  This could tell us the
amplitude 
	of 
	> cross talk per other lane and where it comes from.  Also, if
we run 
	the 
	same 
	> patterns on three lanes and one lane different, we could see
how the 
	other 
	> three lanes combine to effect cross talk on the lane under
test. 
	> 
	> Regards, 
	> m 
	> 
	> -----Original Message----- 
	> From: DAmbrosia, John F [
mailto:john.dambrosia@tycoelectronics.com 
	< mailto:john.dambrosia@tycoelectronics.com> ] 
	> Sent: Wednesday, June 13, 2001 4:21 PM 
	> To: Serial PMD reflector (E-mail) 
	> Subject: CRPAT / CJPAT Pattern Question 
	> 
	> Everyone, 
	> The 10GEA XAUI Interoperability Group met this week, and were 
	discussing 
	the 
	> use of the CRPAT / CJPAT patterns for its testing.  A general 
	observation 
	> was that the same data pattern appear on all 4 lanes
synchronously, 
	which 
	> means crosstalk is not really being testing, which was
probably being 
	> accounted for by connector crosstalk budget of 4%.  Tyco
presented 
	data 
	> 
	
http://grouper.ieee.org/groups/802/3/ae/public/may01/dambrosia_2_0501.pd
<
http://grouper.ieee.org/groups/802/3/ae/public/may01/dambrosia_2_0501.pd
> 
	f 
	> that showed that crosstalk, which resulted from signals
switching 
	in-phase 
	> (i.e. high to low or low to high), could actually improve the
overall 
	> response of the system.  Thus, the resultant eye is improved
and would 
	be 
	> best case, and not even nominal (all adjacent channels quiet).
> 
	> Obviously, there are a lot of system variables that come into
account 
	when 
	> considering crosstalk, but it would seem that we could improve
the 
	harshness 
	> of these patterns by not making all 4 channels have the same
data 
	patterns. 
	> 
	> John D'Ambrosia 
	> Manager, Semiconductor Relations 
	> Tyco Electronics Corporation 
	> 
	> Tel. 717.986.5692 
	> Mobile 717.979.9679 
	> 
	> email - john.dambrosia@tycoelectronics.com 
	> 
	> 

	-- 
	
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	|     |    
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	< http://www.lsilogic.com>       |_____|   
	
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