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PCI ip core

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Visitor
Posts: 6
Registered: ‎07-20-2010

PCI ip core

Why do I have to add the CLOCK_DEDICATED_ROUTE constraint to the example design?

 

[Place 30-574] Poor placement for routing between an IO pin and BUFG. This is normally an ERROR but the CLOCK_DEDICATED_ROUTE constraint is set to FALSE allowing your design to continue. The use of this override is highly discouraged as it may lead to very poor timing results. It is recommended that this error condition be corrected in the design.

 XPCI_WRAP/XPCI_RST1 (IBUF.O) is locked to IOB_X0Y145
  and XPCI_RST2_i_1 (BUFG.I) is provisionally placed by clockplacer on BUFGCTRL_X0Y0
[DRC 23-20] Rule violation (PLCK-12) Clock Placer Checks - Poor placement for routing between an IO pin and BUFG.
Resolution: Poor placement of an IO pin and a BUFG has resulted in the router using a non-dedicated path between the two.  There are several things that could trigger this DRC, each of which can cause unpredictable clock insertion delays that result in poor timing.  This DRC could be caused by any of the following: (a) a clock port was placed on a pin that is not a CCIO-pin (b)the BUFG has not been placed in the same half of the device or SLR as the CCIO-pin (c) a single ended clock has been placed on the N-Side of a differential pair CCIO-pin.
 This is normally an ERROR but the CLOCK_DEDICATED_ROUTE constraint is set to FALSE allowing your design to continue. The use of this override is highly discouraged as it may lead to very poor timing results. It is recommended that this error condition be corrected in the design.

 XPCI_WRAP/XPCI_RST1 (IBUF.O) is locked to G16
 XPCI_RST2_i_1 (BUFG.I) is provisionally placed by clockplacer on BUFGCTRL_X0Y0

 

Xilinx Employee
Posts: 5,894
Registered: ‎08-01-2008

Re: PCI ip core

which version of tools you are using at your end
In previous versions this ERROR was a WARNING, so the implementation phase was not halted. Due to changes iin DRC reporting this is now an Error. it is acceptable to use the UCF constraint suggested in the Error message to demote this to a Warning:
Please check this ARs
https://www.xilinx.com/support/answers/64452.html

Thanks and Regards
Balkrishan
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