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AM335x Dual Ethernet Phy reset

Jithin Shyam
Intellectual 485 points

Dear  Team,

   I have a custom board with AM335x using Dual Ethernet Support, and using phy device LAN8710 SMSC Device.

Ethernet Interface 1  connected in RMII Mode

Ethernet Interface connected in  MII Mode

RMII Phy Address is set to 0:00 in hardware.

MII Phy Address is set to 0:03 in hardware.

When the board boots up, during ethernet phy scans, its detecting the Phy 0 & 3 and its up and run without and issues. but, when i do a soft reset, (reset button)

after the board reset, from the console we find Phy address 0:03 changes to 0:02, this will happens only when soft reset, if we done a power recycle, phy address will stay as 0:03.

Please help me to resolve this issue.

Regards

Jithin

  • 0
    TI__Mastermind 27890 points

    Jithin,

    Are you asserting nRST on the 8710 device as part of your soft reset? If so, I think it likely that PHYAD[0] is not pulled up correctly on your design. This pin, while optional in RMII mode,  is muxed with RXER in MII mode so an external strapping resistor is required to ensure that the desired configuration is latched correctly after a reset (this pin has an internal PD on the LAN8710). Please review sections 3.7 and 5.5.3 of the LAN8710 datasheet for more details.

    It is also possible that your system SW could be setting the Soft Reset bit in the LAN8710 and overwriting the current (hardware strapped) PHY address via the Special Modes Register (0:4 @ 0x18 of LAN8710), but I think it unlikely...Occam's razor and all that.