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RE: Dual-Ethernet


Yes, in theory you can replace the PHY with any MII compatible
PHY. ETRAX also supports SNI compatible PHYs but I don't think
you can get SNI PHYs any more.

In practice there are minor differences between PHYs. Software
modifications is necessary if you need to do any of the following:

1. Set duplex manually to full/half (auto requires no changes)
2. Set speed manually to 100/10 (auto requires no changes)
3. Get the actual speed/duplex used by the PHY.

I strongly recommend to run auto negotiation for both duplex
and speed. 

I don't think anyone has used an Intel PHY with ETRAX. Most 
customers use Broadcom PHYs. The choice of PHY is quite
important since some PHYs fails to autonegotiate with some
other PHYs.

Two sets of signals are used for Ethernet:

MII : The data and control signals
MDIO: Management interface. Serial bus that can be used
to set/get speed, duplex etc.

The ADDR0 signal on the Intel PHY makes it possible to connect
two PHYs on the same MDIO but the MII still has to be separate.
The broadcom PHYs use 3 address inputs and hence it is
possible to connect 8 tranceivers on the MDIO bus. The ETRAX
can only handle one MII interface so the answer to your
question is no.


-----Original Message-----
From: owner-dev-etrax@xxxxxxx.com]On">mailto:owner-dev-etrax@xxxxxxx.com]On
Behalf Of Pijus Chanda
Sent: Wednesday, October 17, 2001 6:27 PM
To: dev-etrax
Subject: Dual-Ethernet

Question about Ethernet configuration:
The ETRAX 100LX uses a standard MII Interface for the PHY part of the
Ethernet. I should be able to interchange the PHY part with any chips,
that are supporting the MII Interface, for example the Intel LXT972. Is
this correct?
Dual Ethernet wit LXT972?
In the Intel documentation it's said, the MDIO Management protocol
allows one controller to communicate between two LXT972A chips. Pin
ADDR0 is set high or low to determine the chip address. Does the ETRAX
100LX support this feature through the MDIO?
Pijus Chanda