[SI-LIST] Re: PICMG3.1 : is length matching really necessary?

No, it is really the skew between two different pairs. The interpair skew 
is 0.5mm between P and N.
The exact relevant paragraph in the PICMG 3.0 specification is "6.2.3.2 
Base and Fabric Interface requirements"


Daniel





"Leonard Dieguez" <ldieguez@xxxxxxxxxx>
28/11/2006 18:21
 
        To:     Daniel PERON/FR/ALCATEL@ALCATEL
        cc: 
        Subject:        RE: [SI-LIST] PICMG3.1 : is length matching really 
necessary?


I think that they are talking about interpair skew between the P and the
N

Leonard. 

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Daniel.Peron@xxxxxxxxxx
Sent: Thursday, November 23, 2006 8:05 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] PICMG3.1 : is length matching really necessary?

Hi all,
In PICMG3.0, there is a requirement for length matching between the
pairs 
of a fabric interface channel : 2.54mm max.
Even for 10G backplane Ethernet type applications (PICMG3.1 /
10GBase-CX4) 
this seems exagerated, as data are aligned at PCS level.
--> in 802.3 clause 48.2.4.2.2 there is a skew budget table, which 
allocates 2UI (=2x320ps) for PCB (board) skew and 18UI for the 
transmission medium (backplane) skew.

Is my understanding of the standard correct or do I miss something?

Thanks for your help.
Regards.

Daniel Peron


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