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DRA821U-Q1: MCU_CLKOUT0 to Ethernet PHY

Kaushal C
Intellectual 350 points
Part Number: DRA821U-Q1

Dear team,

Can you please confirm if we can use external clock source for ethernet phy instead of using clock from MCU_CLKOUT0. Does this cause any difference?

Regards,

Kaushal

  • 0
    TI__Mastermind 38800 points

    Hi,

    Kaushal C said:
    Can you please confirm if we can use external clock source for ethernet phy instead of using clock from MCU_CLKOUT0. Does this cause any difference?

    You can use External clock of 50MHz instead of internal clock from MCU_CLKOUT0 Pin in RMII interface.
    But, This externally generated clock should be routed to both MCU_RMII1_REF_CLK device pin and the external PHY RMII clock input.
    If you are providing required frequency (50MHz), it may not make any difference if you use external clock source or internal clock from MCU_CLKOUT0 (for MCU CPSW2G)

    CLK_EN should be set to 0 from CTRLMMR_MCU_CLKOUT0_CTRL Register if CLKOUT pin is connected to RMII lines.

    Best Regards,
    Sudheer

  • 0 in reply to Doredla Sudheer Kumar
    Intellectual 350 points

    Hi,

    Doredla Sudheer Kumar said:
    You can use External clock of 50MHz instead of internal clock from MCU_CLKOUT0 Pin in RMII interface.

    To clarify, I'm using RGMII and not RMII. So for RGMII no need to route back the clock to processor right?

  • +1 in reply to Kaushal C
    TI__Mastermind 38800 points

    Hi,

    Kaushal C said:
    To clarify, I'm using RGMII and not RMII. So for RGMII no need to route back the clock to processor right?

    Yes, For RGMII no need to route back the clock to processor.

    Basically below will be the connection for RGMII, Tx clock is from MAC to PHY and Rx clock is from PHY to MAC.


    For more details you can refer to Common Processor EVM Board schematic from TI at Link, It has MCU CPSW2G in RGMII interface for your reference.

    Best Regards,
    Sudheer