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Re: MDC and MDIO


As Rich has said before and you correctly say below, there is no
auto-negotiation in 10GbE.
However, there are many useful functions outside of auto-negotiation that still
need registers.

The role of MDIO is the same as in previous generations of Ethernet; it is used
for control and gathering status information from devices.
The details are in the draft, but control of things like loopback and the status
of signals like signal detect may be managed using MDIO.
The frame format for MDIO is also the same as before.  Previously reserved ST
and OP codes are now used to gain access to a much larger number of devices and
So, MDIO communicates to 10GbE devices in a very similar manner as before, and
what it is controlling is also very similar to what was controlled before
(excepting auto-negotiation).

The proposal from which the drafts have evolved can be found in  :
NOTE : Some aspects of the presentation will differ from  the latest version of
the draft.  Obviously, the current draft overrides the proposal.

More general information is at :


satya <satya@xxxxxxxxxxxxxxx> on 07/02/2001 04:36:55

Sent by:  satya <satya@xxxxxxxxxxxxxxx>

To:   stds-802-3-hssg@xxxxxxxx
cc:    (Edward Turner/GB/3Com)
Subject:  MDC and MDIO

I have learnt that in 10 Gb Ethernet there is no Auto-Negotiation.
The role of MDC is MDIO is changed. Is the frame format is also changed
for serial interface.
I want to know HOW MDIO will communicate to PHY and WHAT.


M.Satya Babu,
Design Engineer,
Chip Engines,
Ashoka Boopal Chambers,
email :- satya@xxxxxxxxxxxxxx