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Question abut the DS120BR820 setting

Ian Wang
Mastermind 25085 points
Other Parts Discussed in Thread: DS125BR820

Dear Sir,

I have question abut the DS120BR820 setting.

Table 2 in spec.

It describes that set Pin22 to R and ther re-driver can support PCIE hot-plug.

If I set  pin22 to F, the re-driver can just auto-detect not hot-plug.

Is that right ??

Thanks, Ian.

  • 0
    TI__Mastermind 29635 points
    Hi Ian,

    The RXDET pin (Pin 22) allows the DS125BR820 to enable the channel automatically when a receiver is automatically detected after the DS125BR820 output. You can achieve this auto-detection with either a setting of R or F, but we typically recommend users to set RXDET = F so that the DS125BR820 is continuously testing for Rx detection instead of stopping after 600 ms.

    I do not think RXDET has anything to do with hot-plug. RXDET is used to determine whether an endpoint device is present and minimize power automatically in the event that any of the channels is unused. RXDET can be considered as part of the initialization process.

    The PCIe hot-plug specification describes a method by which an endpoint may be replaced in a running system without turning the system off. From the PCIe specification, a PCIe hot-plug event is designed such that the user MUST notify the system software somehow before installing or removing a PCIe endpoint device. What this means is that the operating system has a way to inform the card driver (in our case, the DS125BR820) that the end-device (add-in card) is about to be removed. This is different from the description of what the RXDET pin does.

    Usually for us, the operating system uses a switch to power down the DS125BR820 before the hot-plug event occurs. This is done by setting PWDN (Pin 52) HIGH, so hot-plug is associated with PWDN, not RXDET.

    Thanks,

    Michael