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TMS320C6678: getting error on HYPERLINK_SERDES_STS register -- EQOVER and EQUNDER

Naoki Kawada
Guru 19890 points
Part Number: TMS320C6678

Hi,

My customer is using Hyperlink in between two C6678s and now having the issue on HYPERLINK_SERDES_STS register.  It indicates EQOVER=1 and EQUNDER=1 with Fully adaptive equalization enabled. First of all, is this fatal error for correct behavior of Hyperlink ? For example, with this state, is there any possibility to get wrong data via Hyperlink ? 

They are watching the following post and also they are reading the keystone serdes user guide. In order to optimize the EQ level, they are trying to control TWPRE and TWPST1 on HYPERLINK_SERDES_CFGTXn registers, but they could not reach to the condition of EQOVER=0 and EQUNDER=0. It seems the link itself is ok, but they has not been able to read the remote Hyperlink configuration registers. We want to know if this EQ errors are critical for the issue.

Best Regards,
Naoki Kawada

  • 0
    TI__Guru* 95265 points
    Hi,

    What is their Hyperlink data rate? 3.125? 6.25 or 10Gbps? Do they use 4 lanes or only 1 lane? What is the software they used? If they try to access the remote side configuration register, what happened? They got Hyperlink hang?

    What is the Hyperlink status register (offset 0x8) and Link Status Register (0x58)?

    Regards, Eric
  • 0 in reply to lding
    Guru 19890 points

    Hi Eric,

    Thanks for you reply. To answer to your questions and some other updates:

    • 12.5G baud  and using 4 lanes. If they use lower baud, for example, 6.25GHz or 3.125GHz,It worked correctly. 
    • Using hyplnk_evmc6678_C66DevLibBiosExampleProject from the latest PDK
    • status register information: 
      0x08 = 0x04400185
      0x58 = 0xFDF0BDF0
    • If the problem happens, the device can get hang.
    • Hyperlink trace length is ~115mm

    Best Regards,
    NK

  • 0 in reply to Naoki Kawada
    TI__Guru* 95265 points
    Hi,

    From the C6678 errata, www.ti.com/.../sprz334h.pdf Advisory 21 HyperLink Data Rate Limited to 40 Gbaud Issue. So you can only run the Hyperlink up to 10G x 4.

    The offset 0x8 showed the local error and remote error, they are critical errors. 0x58 looks good.

    Please run at 10G x 4 speed, clear local/remote error in offset 0x8 and ECC error in offset 0x4c. Then let me know if Hyperlink works. Also monitor offset 0x8, 0x4c if any error accumulation over time.

    Regards, Eric
  • 0 in reply to lding
    Guru 19890 points

    Hi, 

    Ok, they will use Hyperlink with running under 10Gbaud/lane. As per EQUNDER/EQOVER error, is this critical for Hyperlink operation ? Should it be always 0 for correct operation ?

    Best Regards,
    NK

  • 0 in reply to Naoki Kawada
    Guru 19890 points
    What is your thought on EQUNDER/EQOVER error ?

    Best Regards,
    NK
  • 0 in reply to Naoki Kawada
    TI__Guru* 95265 points
    Hi,

    In the Hyperlink example, there is a function called hyplnkExampleEQLaneAnalysis(). It is noted:
    * The result will be 4 ordered pairs, one ordered pair per lane.
    * The first digit in the pair is whether the coefficient is too big;
    * the second digit is whether it is too small. It is possible to get
    * both 0 or both 1s.
    *

    So I felt this under or over equalized wouldn't give much info. You can use this function but trying different precursors and post-cursors to see if you can get a condition that the ECC error counter is 0 over long time.

    Regards, Eric