The SMI interface over the MDC/MDIO communication wires is an interface that is not so common in the general embedded community. Most often this interface is targeted to PHYs and SWITCH fabric components and hosted by connections on the ETHENET MAC or NIC controller. In this manner host side software manages this interface through registers in the Ethernet controller.

Direct interface to the MDC/MDIO lines by a microcontroller would be a pretty easy task to take on and write. Get yourself a couple of good PHY data sheets from the likes of SMSC, MICREL, DAVICOM, or BROADCOMM and read up on how this interface works and then write bit bang code for it. It is similar to SPI in nature of how it works. I would guess that you could write yourself a good working implementation of the master end of the interface in less time that you'll wait for someone to bring around "reference code". And if you got such code you would still have to dig in and make sure it works for your application - an activity that if done in a rigorous manner - can take longer than writing your own.

Michael Karas