RE: XAUI AC coupling
Rich,
Looking at the technologies likely to be used for XAUI implementations,
the preferred DC operating points for transmitters must lie within a
reasonably limited range. If we could agree on what that range should
be, it is still possible that AC coupling the receiver in most cases
would be the only viable solution for supporting the full range of
common mode voltages. Leaving AC or DC coupling out of the spec
however, would allow compliant DC-coupled receivers provided the full
common mode range can be supported also without the caps.
I think the standard will be more successful if coined such that the
coupling method can be regarded as an implementational detail. As seen
from one or two mails on the subject, both AC and DC coupling have
merits of different kinds. I think I've seen only one DC offset (750mV)
suggested (and disputed) What are the other desired transmitter DC
offset voltages?
Best regards Tord.
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Tord Haulin
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-----Original Message-----
From: Rich Taborek [mailto:rtaborek@xxxxxxxxxxxxx]
Sent: Monday, October 02, 2000 22:36
To: HSSG
Subject: Re: XAUI AC coupling
Ali,
That would be a mute point is AC-coupling operation is required and
DC-coupling is allowed in a note which essentially has no teeth,
compliance requirements, etc.
Best Regards,
Rich
--
Ali Ghiasi wrote:
>
> Rich Taborek wrote:
> >
> > Ladies and Gentlemen,
> >
> HI Rich
>
> You also need to ask the people who still want Dc-coupling, how many
> would agree to a common mode
> voltage. Earlier when I proposed a common mode voltage and a method of
> AC and DC coupling everyone
> wanted their own common mode voltage. Without agreeing t to a common
> mode we have no standard and no point to discuss it under 802.3.
>
> Thanks,
>
> Ali Ghiasi
> Newport Comunication
>
> > A recap of which way folks are leaning on this issue:
> >
> > Allow AC or DC-coupling
> >
> > Ed Grivna - Cypress
> > Dawson Kesling - Intel
> > Jeff Porter - Motorola
> > Rich Taborek - nSerial
> > Simon Sabato - Intel
> > Tom Palkert - AMCC
> > Sharam Hakimi - Lucent
> > Fred Weniger - Vitesse
> >
> > Mandatory AC-coupling
> >
> > Vipul Bhatt - Finisar
> > Larry Miller - Nortel
> > Joel Dedrick - PMC-Sierra
> > Richard Dugan - Agilent
> > Justin Chang - Quake
> > Ali Ghiasi - Newport Communications
> > Chris Simoneaux - Picolight
> > Pat Thaler - Agilent
> > Geoff Thompson - Nortel
> > Howard Frazier - Cisco
> >
> > Clearly there's no clear direction. However, as a compromise, I'm not
> > averse to going in the following direction: Specify and mandate
> > AC-coupled operation for XAUI. An note accompanying the coupling text
> > should allow DC-coupled operation in XAUI links which meet all other
> > XAUI specifications. Furthermore the overview and application subclauses
> > must be modified to show cause for AC-coupling is required. The current
> > test strongly suggests that DC-coupling is more appropriate (i.e.
> > chip-to-chip interconnect). What say?
-------------------------------------------------------
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