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DP83822H: Master / Slave

Kai Hsiao
Guru 12675 points
Part Number: DP83822H

HI Sir 

I saw DP83822 have RMII Master and Slave mode

May I know which application have to use Master mode ?

or 

The difference is clock routing only?

I don't understand which application or condition I need to use Slave mode 

Thanks 

  • 0
    TI__Mastermind 23675 points
    Hi Kai,

    For RMII Master, the PHY will operate off of a 25MHz reference clock.
    This clock can either be a CMOS-level oscillator connected to XI pin or a 25MHz crystal across XI and XO.
    When bootstrapped for RMII Master, the PHY will automatically output a 50MHz reference clock that needs to be fed to the connected MAC.

    When in RMII Slave mode, the PHY will operate off a 50MHz CMOS-level oscillator connected to XI.
    This clock must be shared between the PHY and MAC.

    That is the only difference between RMII Master and RMII Slave. It is purely how you supply and route the reference clock.