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C6455 PCI reset issue

UNA
Mastermind 7980 points

Hi,

I have problem about C6455 PCI boot.
The problem is that PCI boot does not sometimes work.
C6455 continue to retry request for read access of the PCI configuration register from the PCI host.

I think that this phenomenon is very similar to the behavior that PCI bad state of errata(Adisory3.1.12[SPRZ234R]).

I will show the details of the board below:


- Circuit structure:

- C6455 Reset sequence:

- Reset timing:


So, I have questions:

1. I think our circuit structure is equivalent to workaround (Fig. 6) of the errata.
    but, would I have to /PRST and /RESET always High?

2. Our board has a short time(4ns) from /RESET deassert to /POR deassert,
    Is this a likely a factor of the errata?


Best regards,
H.U

  • 0
    TI__Mastermind 35645 points
    HI,

    We are working on this post and will let you know the update shortly.

    Thanks & regards,
    Sivaraj K
  • 0
    TI__Mastermind 43660 points
    H.U,

    From the errata advisory, I understand that the internal and external resets should be controlled by the same source and asserted at the same time to avoid PCI lock up issue. It seems like this correlates to the issue that you are facing.

    Yes, you would have to pull the /PRST and /RESET always High. Please try this workaround.

    Regards,
    Senthil
  • 0 in reply to Senthilkumar Srinivasan
    Mastermind 7980 points


    Hi, Senthil

    Thank you for your reply.

    I understood that /RESET and /PRST must be pull-up when device power-on timing.
    It is difficult to modify /PRST on our board, So I tred to pull-up only /RESET.
    but, the problem is not improve.

    I believe that there is no effect of that /PRST is not pull-up because /PRST singal is AND gating the internal /POR signal.

    Is there is something conceivable problem?
    If also /PRST has to pull up when device power-up, please tell me the reason.

    Best regards,
    H.U

  • 0 in reply to UNA
    TI__Guru**** 166411 points

    H.U

    The key here is that /RESET and /PRST must be asserted high the same time to avoid the lock up condition.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Mastermind 7980 points

    Hello, David

    I will try to pull up the /PRST and /RESET, then report the results.
    Thank you.

    Best regards,
    H.U