Re: Link Status thoughts
Howard,
I was led to believe during 1G that ignoring Signal
Detect in favor of a flat-lined PMD output didn't
work because cross talk and other noise sources could
allow the PMA to generate clock and data back to the
PCS. We were told that we had to use Signal Detect
to inhibit our SYNC state machine.
Why has this gone away in 10G? Is this because we're
able to design new PMDs where in 1G we would be using
existing FC PMDs? Do the SONET PMDs currently work
this way?
What about debugging the individual layers? Can the
PMA detect a flat-lined PMD and assume it is because
the PMD has no Signal Detect as opposed to a broken
PMD or perhaps bad etch/solder? Will the PMA have an
MDIO to report such a thing or must it somehow reflect
its status to the PCS or WIS through the generation of
a particular signal (or lack of a signal)?
Thanks,
Ben
Howard Frazier wrote:
>
> General comment:
>
> Pins = Bad
>
> I believe that the limiting amp stage should have a signal detect
> function built into it, and should squelch its output when the
> incoming signal is below the noise floor.
>
> For AC coupled systems, this implies the addition of a bias to
> the PCS receive input so that it doesn't chatter when the
> PMD receive output is squelched. The "flat line" state observed
> by the PCS receiver will be a sufficient indication of a dead link.
>
> We can't rely on MDIO for signal detect reporting between the
> PMD and the PCS. We can rely on MDIO for Link Status (a superset
> of signal detect) reporting between the PCS and Station Management.
>
> Howard Frazier
> DomiNet Systems, Inc.
>
> Ben Brown wrote:
> >
> > Hey,
> >
> > After a discussion some of us had during the editorial
> > meeting yesterday, I thought I'd put some of our thoughts
> > down on paper. There are still quite a few questions
> > buried in these slides. Anyone with comments, please
> > feel free to share them. I'd like to have these comments
> > before the November meeting so we can put a proposal on
> > the table.
> >
> > Thanks,
> > Ben
> >
> > --
> > -----------------------------------------
> > Benjamin Brown
> > AMCC
> > 2 Commerce Park West
> > Suite 104
> > Bedford NH 03110
> > 603-641-9837 - Work
> > 603-491-0296 - Cell
> > 603-647-2291 - Fax
> > 603-798-4115 - Home Office
> > bbrown@xxxxxxxx
> > -----------------------------------------
> >
> >
--
-----------------------------------------
Benjamin Brown
AMCC
2 Commerce Park West
Suite 104
Bedford NH 03110
603-641-9837 - Work
603-491-0296 - Cell
603-647-2291 - Fax
603-798-4115 - Home Office
bbrown@xxxxxxxx
-----------------------------------------