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DP83869HM: Supporting uni-directional fiber interface (TX-only)

Jacob Verschoor
Prodigy 40 points
Part Number: DP83869HM

We want to use the DP83869HM PHY in our design, but for backward compatibility the system must support RGMII to Fiber in TX-only mode. 

Is this possible with this device? Do I need to manipulate the SD signal?

  • 0
    TI__Mastermind 27905 points

    Hello,

    This is an unusual use case of our PHY, so we may not have a fully vetted out solution for your constraint. However, as a potential solution, please try Reg 0xD4[15] = '1' and software restart the PHY (Reg 0x1F = '4000'). Please report back if this helps matters.

  • 0 in reply to Gerome Cacho
    Prodigy 40 points

    Hello Gerome,

    Thank you for your quick answer. 
    Is it true that this is an undocumented register? Can you explain this bit?

    Currently, we are in the design state, I can't check this this year.
    I let you know the results in the future. 

    I'm asking this right now because I still have the freedom to design an external semi-loopback when the device doesn't support this mode. 
    (The data is transmitted to the SFP, but also transmitted to the SIP/SIN pins of the PHY.)

    Best regards,
    Jacob

  • 0 in reply to Jacob Verschoor
    TI__Mastermind 27905 points

    Hello,

    This feature has not been tested, so if you have ability to design a contingency around this, please do.

    Sincerely,

    Gerome