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DP83825I: Customers have doubts about PHY selection, please support, thank you!

Ken Chen39
Intellectual 545 points
Part Number: DP83825I
Other Parts Discussed in Thread: DP83822I, DP83825
  1. What is the difference between “RMII (Master and Slave Mode)” on DP83825I and normal RMII on DP83822I
  2. Are the software common across all TI’s Ethernet PHY? They share the same register map?
  3. What is the official supported Linux kernel?
  • 0
    TI__Expert 5425 points

    Hi Ken,

    1. In RMII master mode, the 50 MHz crystal used for normal RMII is replaced with a 25 MHz crystal. The master mode PHY will generate the 50 MHz clock instead as outputs for other RMII slave devices. This allows you to save space if you are using more than one PHY on your system, as only one crystal is needed. For more details, I have linked an app note that goes over RMII master/slave mode. https://www.ti.com/lit/an/snla101a/snla101a.pdf
    2. Registers 0x00 to 0x1F are the same across ethernet PHYs because of the IEEE standard. Registers beyond those addresses vary across different PHYs, even across TI PHYs. As a result, you will have to conduct the datasheet for specifics.
    3. Here is a link to the Linux drivers for TI's ethernet PHYs. https://www.ti.com/tool/ETHERNET-SW#primary-sw. These should work for any Linux kernel.

    Regards,

    Adrian Kam

  • 0 in reply to Adrian Kam
    Prodigy 105 points

    Hi Adrian,

    Can I say that RMII slave mode is the "normal" RMII interface, and master mode is a special feature on DP83825I?

    I can use it as a normal RMII PHY if I set it to slave mode.

    Regards,

    Edmond

  • 0 in reply to Edmond Hung1
    TI__Expert 5425 points

    Hi Edmond,

    Yes, you can use it as a normal RMII PHY if it is set to slave mode. The master mode is a special feature for the DP83825.

    Regards,

    Adrian Kam