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DS80PCI800 - LInk Bringup Strategy

John Marcolina
Prodigy 40 points
Other Parts Discussed in Thread: DS80PCI800

We are planning to have 2 repeaters on a Gen3 PCIe link. We need 2 repeaters due to the length of the channel. Are there any recommendations or guidelines on how to set the repeater EQ/de-emphasis parameters when we bring up the link?

  • 0
    TI__Genius 13475 points

    John

    What will the length and the media between the source and the first repeater, between the two repeaters and between the second repeater and the sink?

    Mark

     

  • 0 in reply to Mark Sauerwald88474
    Prodigy 40 points

    Mark,

    (I tried responding to this earlier, but it looks like it didn't work. Trying again)

    It looks like this:

     

    Driver – 6” 1775V – repeater – 20” Megtron 6 – repeater – 5-18” Megtron 6 – receiver

     

    The “5-18” range is due to their being different paths for different channels. Also, the channel is of course bidirectional, and so it runs in both directions. The reverse direction can be assumed to be the reverse of the above.

     

    Thanks,

     

    John

  • 0 in reply to John Marcolina
    TI__Genius 13475 points

    John

    With 'only' 40" of trace, and using Megatron 6, you probably only need one repeater.   Using two repeaters often gets tricky, so if it can be avoided, that would be better.  Not being familiar with your setup, I would try to configure the system such that the bulk of the trace is between the source and the repeater, although for a bidirectional link, you probably want to put it in the middle.

    We have characterized the DS80PCI800 using 40" of FR4 trace, so the Megatron 6 should give you some margin even at the extremes of your trace length.

    What may be best is to contact me directly at mark.sauerwald@ti.com, where we can discuss some of the details of your system more freely.

    Mark Sauerwald

     

  • 0 in reply to Mark Sauerwald88474
    Prodigy 40 points

    Hello,

    Another question on link bringup. The data sheet states, "Seamless support for Gen-3 transmit FIR handshake". How can I get more details on this? Does it just mean the device passes the information through to the TX on the far end?

    In general, it seems that having this device in the link will interfere with proper configuration of the transmit settings due to the repeater buffering the signal. If I'm using this repeater, does TX tuning need to be done manually?