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[FAQ] DP83TC812R-Q1: How can I connect PHYs back to back over RMII?

Hillman Lin
Genius 17345 points
Part Number: DP83TC812R-Q1

There are two type of mode that RMII can support: RMII normal mode and RMII Repeater mode:

  • RMII normal mode is also known as MAC to PHY RMII connection. This mode is set as default mode in DP83TC812 so it did not need any pin configuration change.
  • RMII Repeater mode is also known as PHY to PHY RMII connection (PHYs back to back). This mode require a change in pin functionality CRS_DV to RX_DV in DP83TC812. Register 0x0551 bit[4] can convert CRS_DV to RX_DV. Since TX_EN cannot support CRS_DV signal and only support RX_DV signals from the other PHY, changing the functionality of the pin from CRS_DV to RX_DV is required for PHYs back to back mode.

   

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Regards,

Hillman Lin