• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 34 subscribers
  • Views 899 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DS80PCI800 - RXDET function

Kawai
Guru 19785 points
Other Parts Discussed in Thread: DS80PCI800

Hi,

Please let me confirm about the RXDET function.

There are 8 channel for DS80PCI800, I am understanding that these channels can achieve RXDET independently, am I correct ?

Our customer have modes used in 4 lanes and 8 lanes using 2 DS80PCI800. When in 4 lanes, 4channels of the device will be connected but the rest 4 channels are OPEN. We want the device to RXDET active channels and no RXDET to the OPEN channels for the Root Complex.

Best Regards,
Kawai

  • 0
    TI__Guru* 93670 points

    Kawai-San,

    If the device is used in pin mode then RXDET is for all the channels. But if you use SMBUS mode then individually you can set the RXDET termination settings. Did this answer your question?

    Regards,,nasser

  • 0 in reply to Nasser Mohammadi
    Guru 19785 points

    Hi Nasser-san,

    Thanks for your comment.

    No, that was not my question. Please let me ask you again.

    If you use DS80PCI800 in below connection,
    Can Root Complex recognize as 4 lane PCIe, in pin mode ?
    (Root  Complex4-7 will not detect receiver and only Channel 0-3 is active)

    Root Complex0----->+-----------+----->End Point
    Root Complex1----->|                 |----->End Point
    Root Complex2----->|  DS80     |----->End Point
    Root Complex3----->|  PCI800 |----->End Point
    Root Complex4----->|                 |----->OPEN
    Root Complex5----->|                 |----->OPEN
    Root Complex6----->|                 |----->OPEN
    Root Complex7----->+-----------+----->OPEN

    Root Complex0<-----+-----------+<-----End Point
    Root Complex1<-----|                 |<-----End Point
    Root Complex2<-----|  DS80     |<-----End Point
    Root Complex3<-----|  PCI800 |<-----End Point
    Root Complex4<-----|                 |<-----OPEN
    Root Complex5<-----|                 |<-----OPEN
    Root Complex6<-----|                 |<-----OPEN
    Root Complex7<-----+-----------+<-----OPEN

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Mastermind 29655 points

    Hi Kawai-san,

    In pin-mode, the settings for RXDET will apply to all the inputs/outputs, meaning that RXDET is used whether there is an end-point or not. It cannot just be used for Channels 0-3 only, and this behavior is unavoidable as long as you remain in pin-mode.

    With the default RXDET setting, the DS80PCI800 assumes high impedance (no receiver) input until a valid input signal is detected. This high impedance input termination is the same behavior as when the device is set to expect open channels and ignore RXDET. Can the Root Complex identify a 4-lane PCIe by detecting the number of channels that are 50-ohm terminated v. high impedance terminated? If so, then the root complex should be able to see the configuration as a 4-lane PCIe repeater.

    Thanks,

    Michael

  • 0 in reply to Michael Lu (Santa Clara)
    Guru 19785 points

    Hi Michael-san,

    Thank you very much for your reply.

    I am understanding that RXDET function can be ALL Channel ON or ALL Channel OFF in pin mode, but RXDET will work channel independently.

    So, each channels would act, input Hi-Z when no receiver detection and 50-Ohm input termnation when receiver is detected. Am I correct ?

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Mastermind 29655 points

    Hi Kawai-san,

    Yes, that is correct. Assuming RXDET in pin mode is left in its default Float state, channel outputs will test every 12 ms until detection occurs. Termination will remain Hi-Z for that channel until detection. Once detected, input termination is 50-ohm.

    Michael