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AM5728: Shutdown at PCIe Link partner (Master)

Hideaki Matsumoto
Genius 9230 points
Part Number: AM5728

Hi,

I’ve received a question about the PCIe link partner shutdown from my customer.

They’re considering to use their own board with AM5728 under the following conditions.

Is there anything they should be aware of about the operation of the PCIE pin under these conditions?

Is there something like a PCIe communication termination procedure ?

Also, should some treatment be done for the input pin that cannot be pulled down/up due to PCIe restrictions and the output pin where the receiver will be absent ?

Use case of their board

  • Becomes a PCIe slave
  • DC24 drive
  • Can be connected to the board that is the PCIe master
  • REFCLK is generated on the master board
  • Can use DC24V power and can be operated at DC24V without a PCIe master board.
  • Can receive 24V DC from the board that is the PCIe master, but does not give 24V DC
    (That is, when the master operates, the slave also operates automatically, but the slave alone can also operate)
  • The power of the master may be turned off during operation. At this time, the power of itself (slave side board) is not turned off. Also, at this time, since the connector is not inserted or removed, the PCIe pin remains connected to the master side where the power is off. Especially according to the IC specifications on the master side, it is not desirable to input High level to the RX pin of PCIe while the power is off.

Thanks and regards,
Hideaki

  • 0
    TI__Genius 16976 points

    Looking at the PCIe spec, there is a LTSSM state called Disabled that the link can be placed in to make the lanes go into Electrical Idle.

  • 0 in reply to B.C.
    TI__Genius 9230 points

    Hi B.C.,

    Thank you for your reply. Sorry, let me confirm which their questions did your comment answer to ? Is it for Q2 below ?

    Their questions are :

    1. Is there anything they should be aware of about the operation of the PCIE pin under these conditions?
    2. Is there something like a PCIe communication termination procedure ?
    3. Also, should some treatment be done for the input pin that cannot be pulled down/up due to PCIe restrictions and the output pin where the receiver will be absent ?

    It would be appreciated if they can receive any your advice to design the PCIe for prevent a problem in the case of Link partner shutdown.

    Thanks and regards,
    Hideaki

  • +1 in reply to Hideaki Matsumoto
    TI__Genius 16976 points

    I don't have experience with powering down only one side of a PCIe link. However, before removing power from a link partner I would recommend that all PCIe traffic be halted and the link be placed in the Disabled state.