I use ethernet with an AVR32. Connected to a switch with a 1:1 cabel and direct to a network-card with a cross-over cabel. Is it possible to connect two RJ45, wired 1:1 and cross-over, to a single MAC? Of course only one connection can be used at a time, but whatever cable you have you can connect to whatever port, switch/hub or netword-card. Does the unused port must be terminated in some way? Many thanks for your help
>Is it possible to >connect two RJ45, wired 1:1 and cross-over, to a single MAC? No! You cannot connect a RJ45-Jack or Cabel to a MAC. You can connect it to a PHY which is connected to a MAC. Modern ethernet PHY´s support auto-X-over functionality, which automatically detects, whether a crossed oder a straight cable is connected.
Thanks for your help. The phy on my board do not auto-detect the wiring. Only modern GigE-cards must have this feature. Old 100Mbit cards do not. OK, if I wire two RJ45 with magnetics to my single phy, does the unused wires will disturb the wires used? Both RJ45-connectors are still connected to the single phy. Do I have to terminate the unused RJ45-connector? It is only for the convenience of the user. Whatever cable he have and to whatever he want to connect the uC, choosing the correct RJ45-connector and done.
A lot of 100MBit PHYs support auto-x-over! but it´s not a "must", that´s true.. You want to attach TWO magnetics and Jacks to ONE PHY????? That´s (sorry) crap! If you design your own PCB why don´t you use a simple 100MBit PHY with auto-x-over and one Jack (e.g. http://www.micrel.com/page.do?page=product-info/fastether_trans.jsp )