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Ali, Thank you for your comments. I was disappointed that you chose to
use one of the less constructive approaches of engaging in a discussion, which
is to attribute to me a weak argument that I did not make, so that you can then
easily refute it and hold it up to ridicule. No one would seriously suggest that an
interface specification can be written where “the host PCB and the module
PCB can be any length with same set of compliance points.” Your question asking
if that is what I am proposing and the other similar questions are rhetorical and
do not need detailed response. Everyone understands this can not be done. It is further a misunderstanding of
IEEE standards. They are not written for a specific implementation, but rather specify
a generic set of limits against which specific implementations are compared to determine
if they are interoperable. So your requests for specific implementation details
about one module type are inappropriate for the IEEE. This exchange partly illustrates why
we find ourselves in the unfortunate situation where no generic specification exists
for an important electrical interface identified in several 802.3ba PMDs.
From: Ali Ghiasi [mailto:aghiasi@xxxxxxxxxxxx] Chris The appropriate place to for nAUI chip to module
electrical specifications is in 802.3ba, not in other groups such as MSAs.
There are a number of reasons for this. 1. SMF 40GE and 100GE PMDs (LR4 and ER4) identify
nAUI as their retimed electrical interface. The PMD optical specifications are
close to complete, allowing implementers to proceed with specific
implementations that will be interoperable. In contrast, the PMD electrical
interfaces have seen very few contributions. To allow implementers to move forward
with specific interoperable implementations, a generic chip to module nAUI
specification is required. Page 307 Table 88-1 states CAUI is
optional for 100GBase-LR4/ER4. CL83A provides PMA to PMA CAUI electrical
specifications which satisfy this optional 2. MMF 40GE and 100GE PMDs (SR4 and SR10) identify
PPI as their un-retimed electrical interface. Considerable progress has been
made specifying this interface, which will allow implementers to proceed with
specific implementations that will be interoperable. The same should be done
for the re-retimed PMDs. CL85 defines common pin out for the
CR4/CR10 as well as SR4/SR10 and SFF-8436 defines the QSFP module.
SR4/SR10 due to similarity is adopting 3. 802.3ba will have a detailed chip to chip nAUI
specification. Specifying a variation of nAUI in another standard is a
prescription for conflicting interpretations. It is generally a bad idea to
have to look through two standards for the definition of an interface. If another body has solid information on
the 100GBase-LR4/ER4 module definition then they can do much better job of
defining module test points. 4. PMD electrical interfaces have always been
specified in one standard or another. XAUI was specified in 802.3ae; XAUI
was not specified in the XENPAK or X2 MSA. XFI (for XFP) and SFI (for SFP+)
were specified in MSAs, they were not specified in IEEE. The XAUI 802.3ae
specification underscores the problem we will face if we do not include a chip to
module component to nAUI in 802.3ba. XAUI is specified as chip to chip only,
with no allocation for additional connector loss or test points for module
applications. As a result, there is no solid XAUI chip to module specification
anywhere. IEEE CL38 only defined jitter value and
fortunately not th electrical level, if they would have then we would still had
to support 2.4 V swing PECL with 5. IEEE is the most rigorous and public forum for
writing a generic nAUI interface specification which will then enable interoperable
specific implementations. A specification in 802.3ba will have the broadest
possible pool of contributors and reviewers. If the requirements were known. 6. There is no body today, other then 802.3ba, that has the expertise to complete the nAUI specification.
If this is not done in 802.3ba, then many of the same participants who are now
working on the nAUI chip to chip specification will have to organize themselves
into another standards body to write the chip to module nAUI specification. There are a number of arguments that have been raised
against doing the nAUI chip to module specification in 802.3ba. I have listed
some of these, with responses following them. 1. The specification can not be written because we
have no connector model. *** To write the spec, a generic connector model can
be used, based ether on an existing model such as used for XFP applications, or
based on a model provided by connector supplier(s) based on their best estimate
of a nAUI interface connector model. At least one company has such an
estimate model available. In any case, all the limits, such as connector loss
and cross-talk should be specified in general terms (for example such as the
ICR curve used in 10GBASE-KR.) It is then up to the implementers to design the
channel to meet those limits, such as choosing a specific connector. I just can't see how we can make such a growth
assumption, what about if it is really bad proposal because or something not
possible to meet, 2. The specification may not be applicable to future
nAUI applications, for example mezzanine
cards. *** The chip to module specification will be generic,
assuming generic connector, loss, cross-talk, etc, and will have
conservative limits applicable to a broad range of implementations. This
is similar to the chip to chip specification which is not limited to a single
type of IC package implementation. The chip to module nAUI specification will
provide a reasonable starting point for new implementations, and in most cases
accelerate their development. In the worst and unlikely case of not being able
to meet the 802.3ba standard, a new specification will have to be developed
which is no worse then would be the case without an 802.3ba standard. Are you telling me the host PCB and the
module PCB can be any length with same set of compliance points? 3. Since we are late in the 802.3ba cycle and we are
trying to have a complete specification in March, this specification can not be
completed in time. *** It is an unfortunate that the nAUI chip to module
interface, which is central to SMF PMDs, has seen so little contribution
material submitted. Part of this has to do with miscommunication and
conflicting assumptions made by various contributors with respect to what will
get done and where it will get done. Hopefully our poor progress to date will
motive all of us to quickly remedy our past oversights. Adding additional 4 compliance points to
CL83A could delay the project! Chris you are absolutely right that
we have not seen any useful presentation on 100Gbase-LR4/ER4
From: Mike
Dudek [mailto:Mike.Dudek@xxxxxxxx] During today’s XLAUI/CAUI Ad Hoc call
I picked up some action items to E-mail out some items. Here
are these items. 1
There was significant debate as to whether the XLAUI/CAUI IEEE specification
should be just for chip to chi, or whether additional test point specifications
should be included for host/module. Ie whether the host/module
specs for the retimed interface are included in 802.3 or left for development
by other groups such as MSA’s or SFF committee. Jeff volunteered to
ask CFP members their views, however I think it is an appropriate topic for the
complete group. (FYI The non-retimed PPI host/module
interface specs are being developed in IEEE in Clause 86). 2
Detailed specification discussion. Proposals have been made to define
rise/fall times and De-emphasis. To define rise/fall times in a
reproducible manner, particularly for waveforms with de-emphasis the 0 and 100%
levels have to be defined in an un-ambiguous manner. Clause 86 is
using the stable levels on the square wave pattern (the same levels as used for
OMA/VMA measurement). I think this is the best method, as I think
this probably best predicts system performance. Alternatives
are however the peak levels as defined for De-emphasis (see later), or the average
value of the center 20% of the eye diagram (as used to define zero and one
values in the eye diagram). A proposal has been made to define
De-emphasis as the ratio between peak-peak values and the stable one/zero
levels. Again un-ambiguous definitions are required for peak-peak
and stable one/zero. The proposal suggested that the square wave
pattern is used. The stable one/zero levels could be defined
identically to VMA (average value over center 20% of the one and zero levels of
the square wave). Other definitions are possible, but I see no
advantage in creating a different definition. For the peak values
it was suggested that it should be the value at 0.5UI, however on the call zero
time had not been defined. One definition that I think is reasonable is
the zero crossing time of the square wave. Another definition for the
zero time would be the zero crossing time of the 101010 pattern. (however
this has the disadvantage of requiring a 101010 test pattern that is not
presently defined.). Yet another definition could be to use
the mean crossing point as used to align an eye mask. There are
also other possible definitions that do not require establishing an exact zero
time reference. Peak could be defined as the peak value at any time
within an averaged square wave. Peak-Peak could be defined as the
amplitude of a 101010 averaged signal (again however this has the disadvantage
of requiring the 101010 test pattern). Personally I think the peak
value at any time within the averaged square wave is probably the easiest
definition and recommend it’s use unless there are reasons not to do
this. My second choice would be 0.5UI after the zero crossing of
the square wave. Mike Dudek PMTS Standards & Technology JDS Uniphase CO 80027 Tel 303 530 3189 x7533. From: Dear 802.3ba Colleagues, I'd like to schedule the next meeting for the XLAUI /
CAUI Ad Hoc as follows: Friday December 19th 8:30am - 10:30am Dial-in Number (Canada & USA) :1 877
234 4610 Participant Conference Access code: 4405734 # (see
below for additional phone numbers) Presentations should focus on technical details /
values related to the nAUI specification. In particular, I would like to
focus on the channel specification & de-emphasis proposals. Anyone wishing to present, please follow the
guidelines described on the Procedure for Presenters web page: http://www.ieee802.org/3/hssg/public/presentproc.html If you are planning to participate please take a
moment to read the IEEE patent policy available here: http://standards.ieee.org/board/pat/pat-slideset.ppt.
* Participant Conference
Access code: 4405734 # * Dial-in Number:416 883
8981 * Dial-in Number:1 877 234
4610 Best Regards, Ryan Market Manager Analog & Mixed-Signal Products Gennum Corporation Phone: 905 632 2999 x 1610 |