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Tom
The
CJPAT solution seems acceptable. I am unsure of what you are proposing for
CRPAT, but as you pointed out you have other issues with
CRPAT.
John
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]
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]
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
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]
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]
>
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]
>
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]
>
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]
>
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
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
>
>
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mike
Jenkins
Phone:
408.433.7901
_____
LSI Logic Corp,
ms/G715 Fax:
408.433.7495 LSI|LOGIC|
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1525 McCarthy
Blvd. mailto:Jenkins@LSIL.com
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