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DP83822EVM: About Quick Setup

tsuyoshi tokumoto
Expert 2630 points
Part Number: DP83822EVM
Other Parts Discussed in Thread: TIDA-00928

Hello team,

  I have a question about DP83822EVM.

  I understand about the link at startup as follows.

  In the "Operation-Quick Setup" on User's Guide page 7,
  even if the PHY is turned on after a link partner is connected,
  the PHY will be connected with the link partner correctly.

  Is my understanding correct?

Sincerely,
Tsuyoshi Tokumoto

  • 0
    TI__Mastermind 19780 points
    Hi Tokumoto-san,

    Yes, if steps 6, 7, or 8 are mixed up in any order, a connection will still be established with a link partner.

    Best Regards,
  • 0 in reply to Rob Rodrigues
    Expert 2630 points

    Hello Rodrigues-san,

      Thank you very much for your reply.

      I evaluated the Link test with DP83822EVM.
      As you say,the Link was established between the DP83822EVM
      and Link partner(PC) correctly under either condition.

      However,please let me ask you two additional questions.

      After the D4-LED lighted up,when I read the PHYSTS bit0 through
      the SMI,that bit was low.
      In addition,when I read the PHYSTS bit0 after reading BMSR once,
      that bit became high.

      My evaluation procedure is as follows.
        *The jumper pins setting remained the default.

        1.Operation-Quick Setup.
        2.Wait until the D4-LED lights up.
        3.Read the PHYSTS.
             ⇒Result:The bit0 was low.
        4.Read the PHYSTS again.
            ⇒Result:The bit0 was low.
        5.Read the BMSR.
            ⇒Result:The bit2 was low.
        6.Read the PHYSTS.
            ⇒Result:The bit0 was high.
        7.Read the BMSR.
            ⇒Result:The bit2 was high.

      Question1)
          Why is the PHYSTS bit0 low until the BMSR is read once
          although the D4-LED lights up?


      Question2)
         Why is the BMSR bit2 low at the first reading of BMSR?


    Thank you and best regards,
    Tsuyoshi Tokumoto

  • 0 in reply to tsuyoshi tokumoto
    Expert 2630 points

    Hello Rodrigues-san,

    　I would appreciate it if you would give me some advice.

    Thank you and best regards,
    Tsuyoshi Tokumoto.

  • 0 in reply to tsuyoshi tokumoto
    TI__Mastermind 26320 points
    Hi Tokumoto-san,

    The behaviour is captured in Datasheet.

    PHYSTS ( Register 0x010, bit 0)
    Link Status:
    1 = Valid link established (for either 10 Mbps or 100 Mbps)
    0 = No link established
    This bit is duplicated from the Link Status bit in the BMSR register
    (address 0x0001) and will not be cleared upon a read of the PHYSTS
    register.

    Means read of 0x001 is needed to clear this bit of register.


    Regards,
    Geet
  • 0 in reply to Geet Modi
    Expert 2630 points

    Hi Geet-san,

      Thank you very much for your reply.

      I understand that reading the BMSR is needed to update the
      PHYSTS bit0.

      By the way, what about the question2?

      Question2)
         Why is the BMSR bit2 low at the first reading of BMSR?

         Is it necessary to read the BMSR twice to update the BMSR bit2?


    Thank you and best regards,
    Tsuyoshi Tokumoto

  • 0 in reply to tsuyoshi tokumoto
    TI__Mastermind 23675 points

    Hi Tokumoto-san,

    You need to read it twice because the register is a latch-in.

    The first read will be no link since the register is populated when the link is not yet established.

    When you read that register, the register will clear and then grab the updated status.

  • 0 in reply to Ross Pimentel
    Expert 2630 points

    Hi Pimentel-san,

      Thank you very much for your prompt reply.
      I understand your answer.

      My customer begins to design a circuit for a prototype with DP83822.
      Please let me ask you two additional questions.

       Q1)  I understand that the Link status will be immediately reflected in
               the PHYSTS bit0 and the BMSR bit2 when the Link is broken.
               Is my understanding correct?

      Q2)  My customer wants to use a RJMG1BD3B8K1ANR to transformer for DP83822,
              because it has been used in Ethernet for other models(other maker's PHY was used).

              From the electrical specification,I think that the RJMG1BD3B8K1ANR is usable for DP83822.
              As I attached the data sheet of RJMG1BD3B8K1ANR,please let me know if you have any advice.

    RJMG1BD3B8K1ANR.PDF


    Thank you and best regards,
    Tsuyoshi Tokumoto

  • 0 in reply to tsuyoshi tokumoto
    TI__Mastermind 26320 points

    Q1 : Link status is immediately reflected in both PHYSTS and BMSR. However software has to read to clear the status. Next status update is reflected only when last status change is read by software driver.

    Q2. Yes, looks ok. Ensure the connection of center tap is followed as in DP83822 TIDA-00928 or as given in datasheet.

    Regards,
    Geet

  • 0 in reply to Geet Modi
    Expert 2630 points

    Hi Geet-san,

    　I appreciate your prompt reply.
    　Your answer is very helpful for me.


    Thank you and best regards,
    Tsuyoshi Tokumoto