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DP83TC811S-Q1: RECR register(0x15) related

Part Number: DP83TC811S-Q1

Hi Expert,

My customer is using DP83TC811S-Q1 in their project. It shows some failures during the TC8 test. They tried to check the RECR register(0x15). The value they read is always 0. My questions are, 

  • Does TC8 test failure will cause the error count in this register?
  • If not, What does this error indicate?

Thanks!

Ethan

  • Hi Ethan,

    Can customer be more specific with what TC-8 tests they are failing?

    Sincerely,

    Gerome

  • Hi Gerome,

    The specific failure is the cable diagnostics test. The description as below.

    DUT: DP83TC811S-Q1

    Cable fault: TRD_P/M short each other, TRD_P/M short to ground, TRD_P/M short to power

    Precondition:

    • DUT and Link Partner connect to stable power supply
    • DUT require work under normal mode
    • Link Partner in slave mode

    Procedure:

    1. Clear the fault status from cable fault which detected by DUT
    2. After ‘t’ waiting time, read out the cable fault status which detected by DUT
    3. Inject a cable fault during ‘t’ period
    4. After ‘t’ waiting time, read out the cable fault status which detected by DUT
    5. Repeat step 1~4 for each cable fault type(TRD_P/M short each other, TRD_P/M short to ground, TRD_P/M short to power)

    Expect result:

    • The controller can indicate the cable error distance and receive error count

    Actual result:

    • The controller cannot receive the error frame count information

     

    They tried below methods to identify this cable fault, but the result shows the failure for getting the error count. The value they read out is 0.

    -----------------------------------

    Their method to identify the cable fault type and distance which detected by DUT

    1. Write 0x8000 to TDR register 0x001E:
    2. Read TDR 0x001E to make sure the measurement complete(bit 1:0)
    3. Read TDRR register 0x016B to get the result.

     

    Their method to identify the error frame count which detected by DUT

    1. Read RECR register 0x0015 to get the error counter.

    -----------------------------------

     

    Question:

    • 0x0015 in a direct register, as my understanding they can read directly. Please help confirm.
    • For the cable diagnostic test, please help review their test method. Is this the right way to read the error frame information?

    Thanks! 

    Ethan

  • Hi Ethan,

    Please see SNLA291 section 3 for information regarding error count and cable error distance.

    Sincerely,

    Gerome

  • Hi Gerome,

    Thanks!

    I just read it. Their method to access TDR register and identify the cable fault type and distance is correct. They can read out the TDR value, but the RECR register(0x0015) is always 0. 

    So do you know why? 

    Best Regards,

    Ethan Wen

  • Hi Ethan,

    I will need to look at TC-8 standard to verify, but current belief is that for this test, only TDR testing is sufficient, with no error counting required. If MDI pins are shorted to either each other, GND, or power, then line would be dead and there would be no way for PHY to receive any packets, let alone error packets. 

    Sincerely,

    Gerome