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Original question:

Back to back Gigabit Ethernet Phys???

DP83867E: RGMII Back-to-Back mode

Yantao Dong
Intellectual 256 points
Part Number: DP83867E
Other Parts Discussed in Thread: DP83TG720EVM-MC

Question related Back to back Gigabit Ethernet Phys??? - Interface forum - Interface - TI E2E support forums

DP83867_RGMII_Back-to-Back.pdf

This PDF shows the RGMII interface connection between two PHYs in Back to back mode. what I want to know is 

HOW TO DEAL WITH THE MDC AND MDIO?

I think  MDIO may be directly connected together between two PHYs , but which one should provide clk to MDC?

Thanks

Yantao

  • 0
    TI__Genius 17280 points

    Hi Yantao,

    Both of the Ethernet PHYs need an external microcontroller to connect the MDC and MDIO.

    Kind Regards,

    Joe

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • 0 in reply to Joe Vanacore
    Intellectual 256 points

    Hi  Joe

    Thanks for your reply.

    What I am trying to design is a board which is like an ethernet repeater, or a board like DP83TG720EVM-MC,I don't know to much about software about the MDIO configurations, I am checking the possibility to remove external microcontroller, so I still have some questions confusing me. 

    1. MDIO configurations need to be done is  OPTIONAL or MUST？

    2. MDIO configurations need to be done EVERY TIME when start or JUST ONCE？

    3. Does the repeater or DP83TG720EVM-MC work if the MDC and MDIO are LEFT OPEN and with the configuration PRE-FLASHED？

    4. Does the repeater or DP83TG720EVM-MC work if the MDC and MDIO are LEFT OPEN and without any configuration PRE-FLASHED(original chip purchased from TI)？

    Thanks

    Yantao

  • 0 in reply to Yantao Dong
    TI__Genius 17280 points

    Hi Yantao,

    My answers to your questions are listed below

    1. MDIO configurations need to be done is  OPTIONAL or MUST？
      1. You must if want to change default settings
    2. MDIO configurations need to be done EVERY TIME when start or JUST ONCE？
      1. just once or after power cycle 
    3. Does the repeater or DP83TG720EVM-MC work if the MDC and MDIO are LEFT OPEN and with the configuration PRE-FLASHED？
      1. You will need to configure every time PHY powers up
    4. Does the repeater or DP83TG720EVM-MC work if the MDC and MDIO are LEFT OPEN and without any configuration PRE-FLASHED(original chip purchased from TI)？
      1. For basic functionality it will work

    Kind Regards,

    Joe

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • 0 in reply to Joe Vanacore
    Intellectual 256 points

    Hi, Joe

    Thank you very much. 

    More questions.

    what's the exact content of the MDIO configurations? and what functions will loss if without any configuration pre-flashed.

    Thanks

    Yantao 

  • 0 in reply to Yantao Dong
    TI__Genius 17280 points

    Hi Yantao,

    The default register values will be configured after a power cycle so all functions outside of default will be removed.

    The exact content of the MDIO configurations is register configurations.

    Kind Regards,

    Joe

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)