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DP83869HM: SGMII-RGMII Bridge Mode Strapping

Ryan Roberts
Prodigy 30 points
Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869, DP83869EVM

Tool/software:

I am using the DP83869HM in bridge mode, with SGMII connected to the MAC and RGMII connected to the phy as shown below. 

I am getting conflicting information on how to set the strapping on pin 38 to set the direction correctly. 

Per the datasheet, pin 38 needs to be in mode 0 (open) for SGMII to RGMII mode. 

However, from SNLA318 "Understanding different modes of operation in DP83869", it says to set pin 30 to mode 1 (pull-up to VDDIO). 

Can you let me know what is the correct pin strapping? I know there several descriptions of the register settings for this in other forum posts, but I am the hardware designer and I want to make sure the resistors are correct without having to make register changes. 

Would you also update whichever document is wrong to avoid problems like this in the future? 

Thanks, 

  • +1
    TI__Mastermind 30180 points

    Hi Ryan,

    I tested this in the lab on the DP83869EVM. I'm seeing RGMII to SGMII bridge mode with Pin 38 pulled up. When the pullup is removed, the op-mode is SGMII to RGMII.

    I used register 0x01DF to determine the mode of operation. With the pullup present, this register was 0x0003. With the pullup removed the register is 0x0043:

    The datasheet is correct here. I'll look at getting that app note updated in the future.

    Best,

    Shane