Reminder: Serial Attached SCSI PHY Study Group Conference call Monday, June24 2:00 pm - 4:00 pm CDT

Paul Levin levinpa at
Thu Jun 27 10:49:22 PDT 2002

* From the T10 Reflector (t10 at, posted by:
* Paul Levin <levinpa at>
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Dear Mike,

This proposal includes not a few loose ends that will jeopardize any chance
of the scheme operating properly.
1) It does not address how good the 50 Ohm resistors are.
2) It does not address how good the 10 nF capacitors are.
3) It does not address the impedance or bandwidth of the probe.
4) Perhaps items 1) through 3) could be absorbed in a combination of
transmission and return loss specifications.
5) Perhaps easier than a probe would be to implement the probe as an
electrical splitter with return loss and transmission characteristics. The poorer
the input characteristics of a piece of test equipment, the more effort would
be required to create the wide band impedance and transmission matching
networks, or the greater the attenuation to the test equipment port.
6) Even if you get the return loss specification, you must allow for the
possibility that varying lengths of line in a real system will "rotate" the complex
impedance in every possible direction. To check this, one might want to try
using various electrical lengths all with maximum attenuation.
7) Lastly, even if the system works all around the circle, what makes you sure
that it will work in the center? Recall that a classic fix for balky Fibre Channel
connections was to use a longer cable.
8) Wouldn't it be easier to insist on a minimum return loss for the transmitter



Mike Jenkins wrote:

> * From the T10 Reflector (t10 at, posted by:
> * Mike Jenkins <jenkins at>
> *
> Alvin and all,
> Regarding the AI #6 assigned to me at the June SAS meeting in
> Minneapolis (propose a compliance interconnect model for SAS),
> an initial proposal has been uploaded as:
> Regards,
> Mike
> ...
> > 6.    Jenkins to develop test load model proposal: Enhancement to define a
> >       compliant interconnect by which transmitter compliance can be tested
> >       to assure receiver parameters. Status?
> ...
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  Mike Jenkins               Phone: 408.433.7901            _____
>  LSI Logic Corp, ms/AH260     Fax: 408.954.4764        LSI|LOGIC| (R)
>  1525 McCarthy Blvd.       mailto:Jenkins at        |     |
>  Milpitas, CA  95035      |_____|
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> *
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