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TLK105L: Power down the board，if the PRU interface connect to the Switch，the local area network paralysis

user5032636
Prodigy 170 points
Part Number: TLK105L
Other Parts Discussed in Thread: AM5708

Hi

Ours custom board has two 100M pru-eths with TLK105L on AM5708 platform,the hardware design is the same as  TI AM5728IDKEVM board.We found that when we power off the board without disconnect the twisted-pair cable connecting the PRU-ETH to the Swith ,the other board connecting to the Switch could not get IP address immediately.Then we did tests  on TI  AM5728IDKEVM board and we found this issue also happened. Therefore we think it may be a hardware problem of the hareware design or a problem of the TLK105L. 

We wanted to make it clear the reason about this issue.

Hope for your replication.

Thank you.

  • 0
    TI__Mastermind 23675 points
    Hi,

    I am not sure I understand the issue.
    From the description above, you say that you power the board off, but are expecting a response.
    If the PHY is off, data transfer cannot occur.
  • 0 in reply to Ross Pimentel
    Prodigy 170 points

    Dear Ross

    Maybe my description is not clear enough.I wanted to discribe it again.

    There are two PRU network ports on my board. In normal use, the two PRU network ports will be connected to the LAN  through the twisted pair cable, and the PRU network port functions normally. When we power off the board, we find the switch device still displays that the two PRU network ports are connected and the network ports of other devices in the LAN are abnormal. The abnormal network phenomenon is that the device cannot obtain IP addresses correctly.Then,I power on my board，the network ports of other devices in the LAN can obtain IP addresss correctly.

    The other phenomenon is that if my board used a router to access network，it does not influence other device acess to network.

    Yes,I understand the PHY is off,data transfer cannot occur,but why the switch device could identify it and How it affect the network?

  • 0 in reply to user5032636
    TI__Mastermind 23675 points
    Does your board have a CMC on the TD and RD lines?
    The TLK105L has a parasitic path when it is shut down.
    Link pulses received on RD pins can appear on the TD pins and sent back to the host.
    This makes the host think a 10Mbps link is established.
    By using a CMC on the MDI pins, you increase the insertion loss and prevent the reflections from disrupting the communication.
  • 0 in reply to Ross Pimentel
    Prodigy 170 points

    Hi Ross

    My board use  ICMs ,the RJ45 Connector with Integrated Magnetics which consist of   CMC  on TD and RD line. The block diagram of the RJ45 Connector and my SCH design of PRU showed below.

    My 100M PHY is current mode PHY. Are there any problem with my design?

    According to your analysis, I doubt that the performance of the CMC on the RJ45 Connector ,so I can try to replace the RJ45 connector .

    What esle debugged method can I do?

    Thank you so much.

     

     

    AND

  • 0 in reply to user5032636
    TI__Mastermind 23675 points
    Hi,

    For debug please add 10pF decoupling caps on each of the signal lines (TD+/-, RD+/-).