C6455 PCI reset issue

UNA

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

over 8 years ago

0 Sivaraj Kuppuraj over 8 years ago

TI__Mastermind 35645 points

HI,

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

Thanks & regards,
Sivaraj K

0 Senthilkumar Srinivasan over 8 years ago

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 UNA over 8 years ago 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 David (ASIC) Liu over 8 years ago in reply to UNA

TI__Guru*** 139515 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

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C6455 PCI reset issue