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Visitor sm1109
Visitor
6,205 Views
Registered: ‎02-04-2009

how long does it take the trn_lnk_up_n signal to assert?

Hi 

I am starting a project with the PCIe block plus core and according to what I read in the user manuals and the website, I have gathered that the trn_lnk_up_n should assert and only after that I can start any transactions. I have hooked this signal to a led on my board and programmed the board following the steps given. But the led does not give me any indication that the trn_lnk_up_n has asserted. Does the trn_lnk_up_n assert for a very short time during which its not possible to see the led transition or does it stay asserted (in which case nothing is happening on my board)? Is there any other signal which can indicate that the core is ready to start to receive packets?

 

Thanks. 

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3 Replies
Xilinx Employee
Xilinx Employee
6,158 Views
Registered: ‎08-07-2007

Re: how long does it take the trn_lnk_up_n signal to assert?

Hi,

 

In hardware, trn_lnk_up_n will assert  and stay asserted as long as the link is viable. trn_lnk_up_n is active low so keep that in mind with your LED activeness.

 

A few things to try...

1. Also check trn_reset_n - deassertion of this signal tells you three main things - 1. the internal fabric PLL is locked indicating the clocks are good, 2. the MGT lane 0 PLL is locked, 3. the system reset is deasserted.

If trn_reset_n is not deasserting (going high), then you may have a clocking issue

2. If its a multi-lane link and an add-in card, try taping off the upper lanes and force it to a x1. Often, if you have some type of board issue, a x1 will work where x4 or x8 will not.

3. Check that your input reference clock frequency matches that of what you selected when you generated the core - either 100 MHz or 250 MHz

4. Use chipscope to see if trn_lnk_up_n is ever asserting. It may be linking up but when the INIT_FCs DLLP begin, the link may not be that solid which would cause repeated errors and the link to go down. This would happen so fast you probably wound not be able to visible see it go up and down with an led.

 

-John

Visitor sm1109
Visitor
6,086 Views
Registered: ‎02-04-2009

Re: how long does it take the trn_lnk_up_n signal to assert?

Thank you so much...It was very helpful...
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Visitor captainjiang
Visitor
5,351 Views
Registered: ‎04-02-2009

Re: how long does it take the trn_lnk_up_n signal to assert?

did your pc find your board?if trn_lnk_up_n is not asserted,your pc will not find the board!did you resolve the problem?I have the same problem,could you share your experience about this problem?

thanks in advance!!

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