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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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