Hi,
I'm looking for an ethernet PHY which can be connected back to back with another PHY using RMII or MII.
Target application requires support of 10 Mbit/s ethernet speed and half duplex.
I'm wondering if this would even be possible.
SNLA076A gives:
"By connecting two DP83848’s in a back-to-back fashion at the RMII, packets received from one DP83848 may be
transmitted directly by the other DP83848 without need for any additional buffering or control. This method
will not work for half-duplex since there is not a MAC involved to handle recovery from collisions."
I don't understand why collision handling won't work, could someone please explain?.
I thought the back-to-back coupled phys would behave completely transparent regarding the ethernet copper connection (they are working as a repeater).
Referring to the picture below, my assumption is that, if there is a collision data bits will get corrupted and these corrupted bits will propagate over (R)MII back-to-back connection and along to the MACs at the endpoints.
The transmitting MAC recognizes the collision because received corrupted bits differ from transmitted bits and therefore stops transmission.
Surly, the back-to-back PHYs will introduce some latency but as long as the complete round trip time is less than 512 bit times (timing of ethernet spec. regarding collision handling) that should be ok, isn't it?
