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AM5746: PCIe de-emphasis

rei
Mastermind 6155 points

Part Number: AM5746

Hi,

My customers hope to change "De-emphasis" on PCIe.
According to SEL_DEEMP and DEEMPH_LEVEL in PCIECTRL_EP_DBICS_LNK_CAS_2 register on page 6354 of TRM,
This is a Read Field and cannot be changed.
(It couldn't be changed even if I wrote this field.)

Is it possible to change Emphasize?
(1:-3.5dB -> 0:-6dB)


Regards,
Rei

  • 0
    Mastermind 6155 points

    Hi,

    Sorry, I made a mistake.

    SEL_DEEMP fields are Read only in EP register.

    We wrote SEL_DEEMP in RC register, but we couldn't change De-emphasize.

    Is it possible to change Emphasize?
    (1:-3.5dB -> 0:-6dB)

    Rei

  • 0 in reply to rei
    TI__Guru**** 176661 points

    Hi Rei,

    What OS do you use? Do you use the PCIe in RC or EP mode?

    Can you please explain why you want change the emphasize?

  • 0 in reply to Bin Liu
    Mastermind 6155 points

    Hi Liu,

    Thank you for your reply.

    They are using TI-RTOS. AM5746 are connected to each other. (use EP and RC)

    In customer applications, sometimes collectable errors occur. They suspect the signal quality and think that changing emphasis may solve it.

    Regards, Rei

  • 0 in reply to rei
    TI__Guru**** 176661 points

    Hi Rei,

    Thanks for the update. I will route your question to our TI-RTOS expert. Any further response will be directly posted here on this thread.

  • 0 in reply to Bin Liu
    TI__Guru 56475 points

    Hi Rei,

    I talked to out PCIE/Serdes experts, they all think to force the De-emphasis is not a good idea. Can you tell us why you wanted to force the -6db.

    Here is how you can change the De-emphasis selection in pcieSetGen2() of pcie_sample.c:

    /* Setting PL_GEN2 */
      gen2.numFts = 0xF;
      gen2.dirSpd = dirSpd;
      gen2.lnEn   = 1;

      gen2.deemph   = 1;
    #ifdef PCIESS1_X2
      gen2.lnEn = 2;
    #endif
      regs.gen2 = &gen2;

      if ((retVal = Pcie_writeRegs (handle, pcie_LOCATION_LOCAL, &regs)) != pcie_RET_OK)
      {
        PCIE_logPrintf ("SET GEN2/link cap register failed!\n");
        return retVal;
      }

    Ming