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DP83869HM: How to interface a CPU with RGMII pins to the Quectel EC21-A with SGMII pins?

Kar L
Prodigy 70 points
Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869

I am trying to figure out how to connect a CPU that contains RGMII pins to the LTE Module that takes SGMII pins. Would the DP83869 which has a bridge mode work for the conversion? Section 1.4 discuss a RGMII-to-SGMII Bridge option. But I think we need both way conversion so I am not sure how I can both ways to work with DP83869 (RGMII -> SGMII and SGMII -> RGMII). I am in Hardware so I am not familiar with how to configure the registers to set up these modes. Would this connecting work or do I need a PHY between the DP83869 and EC21.?

[MAC (RGMII)]  <-> DP83869 (RGMII <-> SGMII bridge) <-> EC21 (SGMII) 

Our second approach is to use 2 PHYs to make this connection:

MAC (RGMII)]  <-> DP83869 <-> Magnetics <-> DP83869 <-> EC21 (SGMII)

But we are very limited in space. Any feedback would be much appreciated!

  • 0
    TI__Mastermind 18425 points

    Hi Karl,

    The first configuration will work with DP83869 between RGMII-MAC and SGMII-EC21.

    [MAC (RGMII)]  <-> DP83869 (RGMII <-> SGMII bridge) <-> EC21 (SGMII) 

    When the datasheet says RGMII-SGMII bridge, it means that a traditional MAC will be connected to the RGMII side of DP83869 and the traditional PHY will be connected to the SGMII side. The data will flow bi-direction. 

    -Regards

    Aniruddha

  • 0 in reply to Aniruddha Khadye
    Prodigy 70 points

    Hi Aniruddha, thank you for the response and your help. Is there a reference design on how to design with the RGMII-SGMII bridge to ensure our design will work? 

  • 0 in reply to Kar L
    TI__Mastermind 18425 points

    Hi Kar L,

    Unfortunately, there is not reference design for bridge mode. The strap settings for enabling bridge mode is documented in the datasheet. For layout, you would need to follow the same layout guidelines for RGMII and SGMII as you would for any ethernet design that uses RGMII or SGMII interfaces.

    -Regards

    Aniruddha