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DS80PCI102: DS80PCI102

Ranga Narayan
Prodigy 60 points
Part Number: DS80PCI102

Hi ,

I am using DS80PCI102 repeater in my PCIe link.

We notice that the the link will not consistantly go into L2 state whenever it is requested to.

The Tx _EP in the link will remain at common mode voltage during course of time L2 is requested.

On an average out of 100 trials it doesn't go to L2 state in at least 20 trials.

I have attached the scope shot with and without L2. Can someone suggest 

Also find the section of schematic.

If I don't use  repeater, everything is alright.Please let me know if you need any additional details.

Thanks

Ranga

  • 0
    TI__Mastermind 43795 points

    What are the 1.5pF capacitors to GND in the circuit for?  These capacitors are not recommended in PCIe or DS80PCI102 documentation.

    The DS80PCI102 is unaware of any high level PCIe power states. Where is the oscilloscope measurement taken?

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Prodigy 60 points

    Hi ,

    Thank you for the reply.

    Yes, those 1.5 pF are not recommended in PCIe, we have kept them as optional.

    In case we have to filter some noise we will use them, currently they are DEPOP..

    Oscilloscope measurement is taken at the DUT  to Repeater Lane.

    Thanks

    Ranga

  • 0 in reply to Ranga Narayan
    Prodigy 60 points
    FYI, Repeater is in between Host and the DUT ( End Point).
  • 0 in reply to Ranga Narayan
    TI__Mastermind 43795 points

    Hi Ranga,

    Since L2 is a low power state have you tried to also put the DS80PCI102 into a low power state as well using the PRSNT# input?

    Would it be possible to zoom into the point in time when L2 starts?

    Please measure near the DUT and also near the DS80PCI102 so that I can see the DC level on the Rx and Tx pins.

    During L2 or any other period of time when no signal is present on the high speed signals, the DS80PCI102 will simply mute it's own outputs and wait for the signal to return.  When the signal is detected again the DS80PCI102 will return to normal operation within 8 ns.j

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Prodigy 60 points

    HI Lee,

    Refer to the schematic we have PRSNT#  always grounded through 1K Ohm as recommended in the datasheet.

    Isn't this a correct configuration ?

    I can probe near DUT  and analyze L2 startup behaviour.

    Thanks

    Ranga

  • 0 in reply to Ranga Narayan
    Prodigy 60 points
    PRSNT# is not available in PCI Express Mini Card and PCI Express Card.
    It is available only in PCI Express - 1-lane slot.

    We are using PCIe Express Mini and there is no any PRSNT# signal, is there any other handshake signal that can be connected
    into the PRSNT# in the repeater.

    Thanks
    Ranga