Re: Link Status thoughts
Hi Howard,
part of what you suggest here makes sense, but I dissagree with
a different part.
The part I don't like is the idea that the PCS receive should
have a bias to prevent chatter in an AC-coupled connection.
I don't particularly like offset-biased differential connections
because they cause duty cycle distortion of the signal.
I think you suggested the best solution in your first paragraph;
i.e., that being to have the PCS receive also have a signal
detect (peak differential-amplitude detector) and to squelch the
line receiver if there is insufficient amplitude.
Regards,
Ed Grivna
Cypress Semiconductor
>
> 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
> >
> > --
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> > Benjamin Brown
> > AMCC
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> > Suite 104
> > Bedford NH 03110
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> > bbrown@amcc.com
> > -----------------------------------------
> >
> >