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RE: [802.3ae] Clarification on Clause 45


As David pointed out, a device that has both 1 Gbit/s or lowerer PHY
capability and 10 G PHY capabiliity can respond to  both the Clause 22
register space and the Clause 45 register space. There would be no need to
put the Clause 22 registers into the Clause 45 register space. If the ST
bits are 01, then the clause 22 registers are addressed with the clause 22
frame structure. If the ST bits are 00, then the Clause 45 registers are
addressed with the Clause 45 frame structure. 

Note that 802.3ae does not use or support autonegotiation so the
autonegotiation registers would only apply to the 1 Gbit/s (or lower speed)

There isn't any reason to put the Clause 22 registers into the Clause 45
register space. Reserved device addresses are a very limited resource and
are reserved for future use such as the needs of future higher speed PHYs.
One can of course do whatever one wants with the vendor specific devices,
but as there are only two, I wouldn't use that scarce resource for registers
that already have a way to be accessed. 

Pat Thaler

-----Original Message-----
From: Devendra Tripathi [mailto:tripathi@xxxxxxxxxxxxx]
Sent: Monday, April 22, 2002 4:09 PM
To: David Law
Cc: stds-802-3-hssg@xxxxxxxx
Subject: RE: [802.3ae] Clarification on Clause 45

Thanks David,

The "orthogonality of address space" is clear now.

I would like to know what options I have if I want to use uniform Clause45
access and I have mixed PHY for 1G and 10G. Looks like the only option is to
put all Clause22 registers (including autonegotiation ones) in "Vendor"

Please note that this becomes important because the Clause 45 device
definitions are not downward compatible (the bit definition are only for 10G
and above).

I would like to think of a better arrangement (a defined device which could
accomodate all these registers). Any thoughts ?

What about Device 0, (which is marked reserved right now) or 6 ?

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

-----Original Message-----
From: David Law [mailto:David_Law@xxxxxxxxxxxx]
Sent: Monday, April 22, 2002 1:52 PM
To: Devendra Tripathi
Cc: stds-802-3-hssg@xxxxxxxx
Subject: Re: [802.3ae] Clarification on Clause 45

Hi Devendra,

I believe the simple answer is that the Clause 22 register would, as always,
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
register could optionally be placed in the same package (the definition of
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,
example, a implementer manufactured a module that included a 10Gb/s PCS and
Clause 22 registers for a 1Gb/s PHY, as you suggest below, then that
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
other combination they choose so long as the bit in the associated devices
package register are set correctly. It is also perfectly acceptable not to
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
access using the Clause 22 Management Frame Format.

As far as the addressing is concerned, to open up additional address space,
to enable different vendors to supply the different sublayers that form a
port, a second 'layer' of addressing was added above that provided in Clause
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.
in Clause 22 the address consisted of the PHY Address + Register Address. In
Clause 45 the address consists of the Port Address + Device Address +
Address. To differentiate between a Clause 22 access and a Clause 45 access
the MDC/MDIO signals, the Start of Frame pattern is 01 for a Clause 22
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

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