I am developing a custom TX2 carrier board that requires 10/100 Ethernet only, not gigabit. For this application, a non-standard connector will be used that only carries two differential pairs, so gigabit cannot possibly be implemented here. I have some questions about how to hook this up properly.
As far as I can tell, the MD0 pair corresponds to TX (typically RJ45 pins 1-2), and MD1 corresponds to RX (pins 4 and 6). These will be run through magnetics with common-mode chokes on the cable side.
What should be done with MD2 and MD3? These will not be connecting to any magnetics. Should these be looped back on themselves, terminated (if so, how?) or left floating? The particular PHY that is installed on the TX2 will have its own requirements, so I don’t think this is something I should guess at.
Any guidance would be appreciated. Thanks.