OMAP-L138 EMAC report Rx code errors

hi, 

     My OMAP-L138's MII connects with a PHY: Micrel's KSZ8873,

     I have a problem with OMAP-L138 EMAC.

    OMAP-L138 EMAC reports many receive code errors.

    After connect ethernet, the register RXALIGNCODEERRORS is not zero.

    In receive buffer descriptor, sometimes the CODEERROR bit is 1.

   Can any one tell me what the CODEERROR means ?

   When I set the PHY as 10M bps, there are more CODEERRORs than 100M bps.

   Sometimes, packet loss would happen, and happens more frequency in 10M bps.

   Frequency is 2.5MHz when set PHY as 10M bps, lower than 25MHz which set PHY as 100Mbps.

    Why did more CODEERRORs and packet loss hanppen with 10M bps PHY?

   What's the problem with my OMAP-L138 board?

   Thanks.