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The link establish process

mskk12
Prodigy 150 points

Other Parts Discussed in Thread: DP83848I

I am using DP83848I in an application. I found there is a problem in the communication. when connect to the computer,  the computer keep says "connected" and then say "cable unplugged" continuously. I am not sure if this is due to the phy chip or FW. May I know to establish a link (at least to make it not show "unplugged") , we only need the phy chip? or the mac layer must be involved?  

  • 0
    TI__Mastermind 31600 points

    The PHY itself can establish and maintain a link without any interaction with the MAC or firmware.  If the link is going up and down, we should examine the PHY configuration more closely.  To that end, I have a few questions:

    1. For the board with the DP83848I, what board are you using?  Is this a board of your design?  If so, is this a new design?
    2. What is being used for the link partner on the other end of the CAT-5 cable?  Is the computer that reports the link as "connected" and then reports "cable unplugged" connected to the PHY under test via the CAT-5 cable?
    3. Does the DP83848I board have a link LED indication?  If so, what is this LED indicating?
    4. Do you have the ability to read the PHY registers to confirm the device configuration?

    Patrick

  • 0 in reply to Patrick OFarrell
    Prodigy 150 points

    Hi Patrick, thanks for the reply. If the PHY itself can establish and maintain the link, then very strange if I do not load any firmware in the board, i.e., no mac layer involved, the pc side just said "cable unplugged" . The board is our new design, the PHY connects to our cpu. The PC is used for testing at the other side of the CAT-5 cable. There is no LED indication but we have the ability to read the PHY register after the FW is loaded. 

  • 0 in reply to mskk12
    TI__Mastermind 31600 points

    I am not sure why the PC on the other side of the CAT-5 cable would indicate that the cable is unplugged, but I think the thing to do is to understand the functional state of the PHY.  I have a few questions to help clarify the functionality.

    When you say there is no LED indication, do you mean that the LED on the board is not lit or do you mean that there are no LEDs on the PHY board? 

    Does the PC ever identify that a cable is plugged in and a PHY is present?  After firmware is loaded, perhaps?

    Patrick

  • 0 in reply to Patrick OFarrell
    Prodigy 150 points

    Hi Patrick, the problem has been solved, basically it is due to the signal voltage level not match between the transmitter and the receiver, since we are using direct connection and without any transformer. Thanks for the help.