# An ethernet PHY chip speed support

I found ENC28J60 Ethernet PHY chip. The specifications say that the Physical Network Type is '10BASE-T' on the one hand, but on the other hand the data rate is '10 Mbit/s, 100 Mbit/s, 1000 Mbit/s'.

As far as I know, a 10BASE-T chip can not support a data rate of 1Gbit/s ! Moreover, the 10BASE-T doesn't support Full-duplex, but the specifications say that the Communication Mode is 'Full Duplex, Half Duplex'.

• BTW the ENC28J60 is not a "PHY chip", it's a complete ethernet controller. – Peter Green Nov 12 '15 at 22:45

From the datasheet

• Fully Compatible with 10/100/1000Base-T Networks
• Integrated MAC and 10Base-T PHY
• Supports One 10Base-T Port with Automatic Polarity Detection and Correction
• Supports Full and Half-Duplex modes

So, it is 10mbps FD (and yes, 10baseT supports full duplex, at least some cards do) and, as all 10baseT devices is compatible with newer networks.

The first page of the datasheets says:

• Fully Compatible with 10/100/1000Base-T Networks
• Integrated MAC and 10Base-T PHY
• Supports One 10Base-T Port with Automatic Polarity Detection and Correction

So it's a 10 Mbit/s 10Base-T device but is compatible with the other standards so you can connect them together and get operation at the lower speed.

You shouldn't rely on the search parameters that appear on supplier parametric search pages, they often seem to contain errors or information that is misleading.

• I would consider that comment in the datasheet seriously misleading. 10BASE-T, 100BASE-TX and 1000BASE-T are seperate protocols which are usually combined with autonegotiation but don't have to be. In particular interfaces that support 10 gigabit don't support 10 megabit in my experiance. – Peter Green Nov 12 '15 at 22:25