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code-word alignment location


I thought I'd throw in a response to your aside using a new thread.

> Una Quinlan wrote:
> [ Aside: Does PCS codeword alignment belong in the PMA/WIS or the PCS?].

In 1000Base-X, code-word alignment (to the comma) occurred in the PMA.
With a break down (from the Uni-PHY proposal) of PMD - PMA - WIS - PCS,
the PMA cannot provide alignment. The WIS needs to align on A1/A2. From
this, the WIS provides byte aligned data to the PCS. If the PCS
is 64b/66b, this byte alignment is useless and 66b alignment is done
to the 1/0 or 0/1 sync bits. The PMA can't participate in any of this
because the WIS is optional and both the WIS and PCS require different
alignment mechanisms. Implementations can do anything they want but the
standard needs to keep these separate.


Benjamin Brown
Router Products Division
Nortel Networks
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