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Original question:

DP83TC811S-Q1: link-up status register

DP83TC811S-Q1: unlink sometimes of DP83TC811S-Q1

Betty Guo
Expert 7300 points
Part Number: DP83TC811S-Q1

Hi team,

customer read reg 0x0133 bit 12 to check if the PHY is link. sometims it will report unlink， and restart the device, it can recovery.

which register can be used to read the link status? I found a similar issue in the bleow link, but I don't know to fixed.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/916357/dp83tc811s-q1-link-up-status-register/3438737?tisearch=e2e-sitesearch&keymatch=DP83TC811S-Q1%25252520unlink#3438737

the questions are :

1. what's the difference between 0x0001 bit 2 link status and 0x0133 bit 12 link status? does it the same?

2. any others methods can be used to check the link status? 

3. do you have other suggesitons for unlink issue?

thank you

  • 0
    TI__Expert 5425 points

    Hi Betty,

    Here are my responses to your questions:

    1. There is no functional difference between those two link status bits. The only difference is that 0x0001 bit 2 needs to read twice in order to get the correct status since it is a latch low bit.
    2. Other than those two bits, the LED_0 pin would be the other method to check the link status.

    I have several questions regarding your issue:

    1. Does the customer see this issue on just one board or multiple boards?
    2. Are there any issues with transmitting/receiving data after the reset?
    3. What is the length of the cable that the customer is using? Can they try with a shorter cable and see if they have the issue?
    4. Is the customer resetting through the RESET pin, or through register write? If it is register write, is it hardware reset (0x001F, bit 15) or software reset (0x001F, bit 14)?
    5. Can you check the bootstrap resistors and ensure that the voltages are within the bootstrap thresholds detailed at the end of section 7.5 of the datasheet? Also, can you check to make sure none of the strap settings are set to a reserved mode?
    6. Is the cable connected to the board before it is powered-up? If so, can you ensure the power-up timing diagram (figure 9, pg. 20 of the datasheet) is being followed?

    Regards,

    Adrian Kam