Re: Link Status thoughts
Hi Ben,
this all depends on if this interface is AC or DC-coupled. Howard
implied in his original email that his interface could be
AC-coupled. If AC-coupled, then yes I think a signal-detect
is appropriate.
-Ed Grivna
> Ed,
>
> Ed Grivna wrote:
> >
> > 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.
> >
>
> By this, do you mean the PMA receive? The PCS receive is the
> XSBI bus and the PMA would drive that to the appropriate voltage
> levels whether it had a strong signal at its inputs or a weak one.
>
> Ben
>
>
> > 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
> > > >
> > > > --
> > > > -----------------------------------------
> > > > 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@amcc.com
> > > > -----------------------------------------
> > > >
> > > >
>
>
> --
> -----------------------------------------
> 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@amcc.com
> -----------------------------------------
>