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AR# 44867

13.x PlanAhead - "[Constraints 5] Cannot loc terminal 'sys_clk_p/n" at site XX, Illegal to place instance ..."

Description

Errors similar to the following occur when elaborating the design in the PlanAhead tool:

"[Constraints 5] Cannot loc terminal 'sys_clk_p' at site H6, Illegal to place instance i_PCIeTop/refclk_ibuf on site H6 ["pcie.ucf":87]"
"[Constraints 5] Cannot loc terminal 'sys_clk_n' at site H5, Illegal to place instance i_PCIeTop/refclk_ibuf on site H6 ["pcie.ucf":88]"
"[Constraints 5] Cannot loc instance 'i_PCIeTop/refclk_ibuf' at site IBUFDS_GTE2_X0Y0, Site IBUFDS_GTE2_X0Y0 is not bonded ["pcie.ucf":102]"

Solution

These critical warnings do not cause any issue when the design is implemented, so they can be safely ignored. 

 

 However, there is a similar warning message to that mentioned in (Xilinx Answer 43315)

The issue described there has been fixed in the PlanAhead 13.4 software, but in earlier versions it did result in constraints being ignored. 

You should review the pad report to verify that the ports are correctly placed. 

 

The issue outlined in the Article Description above is visual only and does not affect the implementation of the design.

As a result it will not to be fixed in the current ISE software. 

However, it is scheduled to be fixed in the next generation of Xilinx software.

AR# 44867
Date Created 03/02/2012
Last Updated 08/11/2014
Status Active
Type General Article
Tools
  • PlanAhead - 13.1
  • PlanAhead - 13.2
  • PlanAhead - 13.3
  • PlanAhead - 13.4