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DP83869HM: How to start PRBS without BIST?

Yansheng Yue
Intellectual 370 points
Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869

Tool/software:

Hi, I'm using DP83869 as a media-converter. Now I need to send some data just at linkup. I think PRBS function can give what I need. But I can not received any packet on the other side.

The topology I used is as follows:

PC1-->media-converter with DP86869-->fiber-->TP Link media converter-->PC2

Packets between PC1 and PC2 can be sent and received correctly in normal operation. Now I need send a few data from DP83869 to PC2 just at beginning with PRBS.

I just write reg 0x16 with 0xF000, where loopback not needed. But I can not receive any packet at PC2. So two questions:

(1) Do I need to config other registers besides reg 0x16 if I do not use loop back and just send out some data?

(2) Does PRBS works if DP83869 in media-converter mode? And if it works, is the PRBS enable register address still 0x16?   

Thanks.

  • 0
    TI__Mastermind 25028 points

    Hi Yansheng,

    Thank you for sharing the setup details - this write 0x16 = 0xF000 is correct to enable PRBS generator.

    I have some clarifying questions:

    • How are packets being being received on PC2 (Wireshark?)
    • Can you probe pins on the fiber and copper sides to confirm if there is data on the line?
    • If running Wireshark on PC1, do you see any activity on copper side with PRBS enabled?

    Best regards,

    Evan

  • 0 in reply to Evan Mayhew
    Intellectual 370 points

    Hi Evan, Thanks for your reply.

    Yes, I acquire packed on PC2 with wireshark.

    It seems there's no data waveform on either lines.

    I did not see any activity on copper side on PC1.

     Best regards,

    Yue

  • 0 in reply to Yansheng Yue
    TI__Mastermind 25028 points

    Hi Yansheng,

    I was mistaken, it appears additional register writes are required to have PRBS transmission activity on copper side.

    Here is the script that allowed me to see PRBS activity on copper in media conversion mode:

    Reg Addr | Value
    00FE E720
    0000 0140
    0010 5028
    0016 0004
    0016 F004

    Please let met know if you can see activity on PC1/PC2, or when probing the lines directly after programming this script.

    Thank you,

    Evan

  • 0 in reply to Evan Mayhew
    Intellectual 370 points

    Hi, I got data now after config the registers as your script. It seems that BIST must be enabled before enable PRBS.

    Thanks.