100Mbits/sec Ethernet over twisted pair

There is a new Ethernet PHY coming out. It is primarily geared towards automotive but I could see it moving into the embedded industrial market quickly. It works with the standard MII ethernet output. It has a speed of 100Mbit/sec up to 15M cable length over a single unsheilded twisted pair.

More info here: [url]TJA1100HN | Automotive Ethernet PHY Transceiver | NXP Semiconductors


So the deal here is that it’s BroadR-Reach, which is a different physical layer than “normal” Ethernet. It uses a single twisted pair for full-duplex communication, instead of 100BASE-TX’s half-duplex per twisted pair. It does this by halving the signal bandwidth. It’s specifically designed for automobiles, where the primary goal is reduced interference.

It’s not interoperable with “normal” Ethernet, meaning, if you try to plug it into your home network, it’s not gonna work…

It’s already in use by at least one car manufacturer, which uses it for all the camera related stuff.
So I guess there are other PHY’s out there, which can be used from Micro Controllers.
I also heard about Gateways, translating from 2 wire to classic 4 wire Ethernet.

If my remeber the drawings right, even my car should have it.

I’m not sure there’s any advantages over “normal” Ethernet, unless you had a specific need for interoperability with BroadR-Reach stuff, or the resilience against interference.

And, of course, less wiring. If you had a lot of devices spread about an area it could be really nice to be able to control four off a single ethernet network cable instead of running a cable for each one.

In a car wire harness it’s all about less and more simple wires.
You have no idea how many Pins a car seat or door connector has in a premium car nowadays.

The PHY that I linked uses a standard MII interface to an ethernet controller or ethernet switch controller so it should be very easy to implement with existing silicon. I wonder if this is a precursor to replacing CAN bus in the future. With as much info that is being thrown around the CAN bus I would think a jump from 1Mbit/sec max to 100Mbit/sec would be welcome improvement.

Anything not requiring high bandwidth would remain CAN, I assume, since you only need two wires total, instead of two wires per device?

I think the spec also puts power on the same pair so you can drive a whole sub system with just 1 pair of wires.

Everything that is safety related will stay CAN and eventually FlexRay for a while.
Not sure how deterministic 2 wire Ethernet is, but CAN is currently so well known and reliable that no car manufacturer would switch so easily.
I often have to browse through CAN message catalogs of several manufacturers. There is so much going on on These busses.