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Re: [802.3ae] Clarification on Clause 45

Hi Devendra,

I believe the simple answer is that the Clause 22 register would, as always, be
put in the (10/100/1000Mb/s) PHY which they monitor/control. This could be a
totally separate PHY however Clause 45 makes the provision that these Clause 22
register could optionally be placed in the same package (the definition of the
term package is vendor specific and could be a chip, module or other similar
entity) as one of the 10Gb/s Sublayers if the implementer so chooses. If, for
example, a implementer manufactured a module that included a 10Gb/s PCS and the
Clause 22 registers for a 1Gb/s PHY, as you suggest below, then that implementer
would indeed set the Clause 22 registers present bit (bit 3.5.0) in the PCS
devices in package register. The implementer is of course free to implement any
other combination they choose so long as the bit in the associated devices in
package register are set correctly. It is also perfectly acceptable not to 'mix'
these devices and have a totally separate 10/100Mb/1000Mb/s PHY with its
associated the Clause 22 registers. In all cases these Clause 22 register are
access using the Clause 22 Management Frame Format.

As far as the addressing is concerned, to open up additional address space, and
to enable different vendors to supply the different sublayers that form a single
port, a second 'layer' of addressing was added above that provided in Clause 22.
This additional 'layer' is called the Device Address. In addition, what was
called the PHY address in Clause 22 is called Port Address in Clause 45. Hence
in Clause 22 the address consisted of the PHY Address + Register Address. In
Clause 45 the address consists of the Port Address + Device Address + Registrar
Address. To differentiate between a Clause 22 access and a Clause 45 access on
the MDC/MDIO signals, the Start of Frame pattern is 01 for a Clause 22 access
and 00 for a Clause 45 access. These two Start of Frame pattern provide two
totally non overlapping address maps.

I hope this helps.

Best regards,
  David Law

"Devendra Tripathi" <tripathi@xxxxxxxxxxxxx> on 22/04/2002

Sent by:  owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx

To:   <stds-802-3-hssg@xxxxxxxx>
Subject:  [802.3ae] Clarification on Clause 45


Could some one clarify which device to put Clause 22 registers in, if they
are present?

If the answer is that they need to be mixed in specific device (say PCS),
how should one map the 16 registers of Clause 22 (including autonegotiations
ones). In this case, I presume, I need to set the bit 0 of register 5 of the
given device (say PCS) to '1'.

Also, when we say (D4.3, page 185, line 9) that MDIO address space is
orthogonal to MII register space, it is not clear how it is so.  Could
someone explain that ? As I see it, we have replaced device address by port
address and register address by device address. But this by itself, does not
make it orthogonal (unless we say that a fixed device, say, device 0 on any
port is defined as MII device).

Devendra Tripathi
CoVisible Solutions, Inc
90 Great Oaks Blvd #206
San Jose, Ca 95119
Tel: (408)226-6800,
Fax: (408)226-6862