Re: XAUI update from Interim meeting
Dawson, et al,
Thanks much for your summary on the XAUI spec changes. I have
a comment/question concerning the summary item stating: "The
templates were centered in the data eye and not allowed to float."
Unless I misunderstand, this change causes an inconsistency in
the specification. In Fibre Channel, at least, eye masks (or
templates) have been defined such that the left-most vertex is
one half the total jitter (i.e., TJ/2) from the left edge of the
bit period (i.e., at 0 UI). The right-most vertex is symmetrically
TJ/2 from the right edge of the bit period (i.e., 1 UI), as shown
in my crude character graphics below (if you have fixed-width font).
_______ ___________
\ / \
\ / \
\ :<- TJ/2 ->:<- TJ/2 ->: / \
\: : :/ \
\ : / \
/ : \ /
/ : \ /
/ 0 UI \ /
/ (bit \ /
________/ boundary) \___________/
If the further constraint is added that 0 UI must be the mean of
the jitter (i.e., zero crossing) distribution, then that FORCES a
mask failure if the distribution is skewed, as it generally is in
copper transmission media.
The practice in Fibre Channel (for copper media) has been to freely
adjust the X position of the waveform. This permits a waveform with
jitter approaching the spec limit of TJ to fit legally on the template.
The proposal to constrain the mean of the distribution to be at 0 UI has
been voted down several times in the Fibre Channel jitter working group.
If I am missing something, I would appreciate being clued in.
Regards,
Mike Jenkins
"Kesling, Dawson W" wrote:
>
> Attached is a summary of XAUI progress and issues for those of you who could
> not come to the Interim meeting last week. All changes and refinements will
> be included in draft D3.1 due to be posted to the 802.3ae web site by 6/11.
>
> If you have questions that aren't answered in the attached summary and can't
> wait until the draft is posted, please send them to the reflector audience
> in general so that other attendees can help me answer them. I probably can't
> respond quickly to ALL the questions that might otherwise be sent to me
> personally!
>
> Thanks to all who participated so helpfully in St. Louis last week. Special
> thanks to Anthony Sanders of Infineon and Tom Lindsay of Stratos Lightwave
> for their extra effort on XAUI jitter leading up to (and after hours during)
> the Interim.
>
> -Dawson Kesling, Intel
> Editor, Clause 47
>
> <<St_Louis_summary.ZIP>>
>
> ------------------------------------------------------------------------
> Name: St_Louis_summary.ZIP
> St_Louis_summary.ZIP Type: application/zip
> Encoding: Base64
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