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DS125DF111: PCIe and SATA/SAS Support

Brian Gosselin
Expert 4745 points
Part Number: DS125DF111
Other Parts Discussed in Thread: DS110DF111, DS125BR111

Hello,

I'm starting an e2e thread for my customer to be able to ask follow-up questions regarding our DS125DF111.

Our initial feedback after working with Lee is that PCIe and SATA/SAS is not supported by the DS125DF111 or DS110DF111 (even while in bypass mode).  The protocol will be broken by installing the retime.

We recommended our DS125BR111 (linear equalizer without any retiming), which can compensate for ~8-10dB of PCB trace attenuation and for protocols up to 12.5Gbps.

Follow-up question:

  • What in the PCIe and SAS/SATA protocols causes issues?  Is it with the link training or the receiver detection?

Thank you in advance for your support.

Best Regards,
Brian Gosselin

  • 0
    TI__Mastermind 43795 points

    Hi Brian,

    There are a few issues with both specifications.  Link training and receiver detection are included in the list.

    Since these retimers do not snoop the protocol, they will not participate in the link training requests.  This will break the feedback loop and lead to unpredictable results.

    For SAS/SATA the OOB signaling cannot be reproduced accurately at the retimer output.

    For PCIe anytime the link goes idle, the retimer would miss 100’s of bits while reacquiring lock.

    Regards,

    Lee  

  • 0 in reply to Lee Sledjeski
    Prodigy 10 points
    If the retimer functionality is turned off(bypassed) can PCIe be made to work?
  • 0 in reply to Pavel Gilenberg2
    TI__Mastermind 29655 points
    Hi Pavel,

    If the retimer functionality is turned off, this may be possible, though at that point you may find things significantly simpler by selecting a corresponding redriver device such as the DS125BR111, which is more ideal for link-training standards such as PCIe Gen-3 and SAS-3.

    Thanks,

    Michael