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DS90UB954-Q1: show the bit error rate

Roy Chou1
Genius 16810 points
Part Number: DS90UB954-Q1


Hi Team,

We have two FPD-link cable and would like to compare these two cable. After doing the S parameters simulation, we know one of cable is better and we also do the MAP and the result is also match.

And MAP only show the diagram, but we would like to know bit error rate. Could you let me know if there is any register setting could indicate the bit err rate?

Regards,

Roy

  • 0
    TI__Mastermind 30710 points

    Hi Roy,

    You can verify the BER using the BIST functionality. The LOCK, PASS, and CMLOUT output functions are available during BIST mode. For any link failures or data corruption, the best indication is the contents of the error counter in the BIST_ERR_COUNT register 0x57 for each RX port.

    See Section 7.5.12 FPD-Link BIST Mode in the UB954 datasheet for more information. Also, see page 16 in the attached App Note for a more in-depth look into BIST mode: https://www.ti.com/lit/an/snla267a/snla267a.pdf?ts=1626800742931&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDS90UB954-Q1

    You can also monitor the PASS pin in real-time, to see any drops in the PASS signal, which indicate error. You can configure when PASS is asserted/deasserted through registers 0x7D and 0x0C.

    Best,

    Justin Phan

  • 0 in reply to Justin Phan
    TI__Genius 16810 points

    Hi Justin,

    Thanks for your reply. According to this file, the block of “Check for Errors” uses 0x54 for checking BIST Error Count. However, you also suggest us to check 0x57’s results. Could you please help to share what these two count different? I assume this procedure should use 0x57 but not 0x54. Thank you.

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Mastermind 30710 points

    Hi Roy,

    The 0x54 register is in the connected UB953 serializer and counts the CRC errors detected during BIST. These are errors that occur during Back Channel transmission (Deserializer -> Serializer). The 0x57 register is in the UB954 and counts the BIST errors that occur during the Forward Channel transmission (Serializer -> Deserializer).

    Best,

    Justin Phan