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Original question:

DP83TC811R-Q1: converting from 100BASE-T to 100BASE-T1 or 1000BASET to 1000BASE-T1

DP83TC811R-Q1: 100BASET to 100BASE-T1 interface with DP83TC811 and DP83826E

Bo Liss
Prodigy 20 points
Part Number: DP83TC811R-Q1
Other Parts Discussed in Thread: DP83TC811EVM, DP83826E,

I want to make an interface similar to the DP83TC811EVM  between 100BASE-T and 100BASE-T1 but with DP83826E instead of DP83822. The evaluation board uses the RGMII interface which is not present on the DP83826E and I have to use either the MII or the RMII interface.

If I want to connect a DP83TC811R-Q1 to a DP83826E using the MII interface I connect RX to TX and RX_DV of one PHY to TX_EN on the other. But what about the clocks? In MII mode both RXCLK and TXCLK are outputs. In the evaluation board DP83TC811EVM RXCLK on one PHY is connected to TXCLK on the other PHY but this uses the RGMII interface where TXCLK is an input. 

Or do I have to use the RMII interface to connect them together? In that case TXCLK and RXCLK is not used. What about the clocks in this mode? Do I need to have the same clock source for both in order to have them syncronized?

  • 0
    TI__Mastermind 39895 points

    Hello,

    We have no data for back-to-back MII use case, so you may need to validate yourself if you go down that route.

    Regarding RMII back to back, there are two PHYs. One will be designated as "master" and the other as "slave". The master PHY will be need to be supplied by a 25MHz signal, which it then outputs a 50MHz signal. This signal is used for RMII communication and must be connected to the slave PHY's clock input, XI. The slave PHY must be initially configured (via strapping) to RMII slave as to accept the 50MHz. 

    Sincerely,

    Gerome