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DS80PCI800 issue

Thomas Chang15933
Expert 4770 points

Dear Team:

  In DS80CI800 datasheet,

Could I always force RXDET to high for 50 ohm? What's the side effect?

  • 0
    TI__Mastermind 43795 points

    Hi Thomas,

    The RXDET circuit is generally  forced to 50 ohms in non PCIe applications.  SATA/SAS or XAUI are some examples.

    For PCI Express I recommend using automatic RXDET functionality if the system configuration is supports "hot plugging" and/or contains an Add-In-Card slot which can be populated with different lane-width PCIe functions.  Only lanes with a valid PCIe endpoint should be terminated, lanes without a valid endpoint should be left floating so the root complex can properly configure the system.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    TI__Expert 4770 points
    Dear Lee:
    THank you.
    Our customer reply it as below.

    ======
    I saw Gen3x8 link in one of 162 AC power cycles. Do you think it is worth trying it to force RXDET to high? If it works,could I always set it to high? In most cases, it can be gen3x16 but there is still low link width.So,I shouldn't use "stably".
  • 0 in reply to Thomas Chang15933
    TI__Mastermind 29655 points

    Hi Thomas,

    RXDET can be tied high if you can assure in your system that a receiver will always be present. The main purpose of the RXDET pin, in addition to the comments Lee made above, is in situations where a hot-plug event may occur between the repeater Tx and the endpoint device.

    Thanks,

    Michael