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AR# 34635

Place - "ERROR:Place:866 - Not enough valid sites to place the following IOBs"


The following error occurs when the DRC checks in the placer detect that an insufficient number of IOB sites are available for the IOSTANDARD specified in the message body:

ERROR:Place:866 - Not enough valid sites to place the following IOBs


Solution 1:
This scenario can occur if you are specifying an IOSTANDARD and there are not enough sites in the device fabric which are compatible with the specified IOSTANDARD.

Please consult the user guide for the device you are targeting to ensure that there are sufficient compatible IOBs.

Solution 2:
This scenario can occur if you lock an I/O to a bank without specifying an IOSTANDARD and the bank has had its IOSTANDARD redefined by a different constraint.

If your design requires specifying an IOSTANDARD other than the default, ensure that you are applying this IOSTANDARD to all of the I/O pins constrained to that bank.

Solution 3:
This scenario can occur in Spartan-6 devices if using LVPECL IOSTANDARD.

LVPECL requires that VCCAUX is 3.3v.

But by default VCCAUX is 2.5v.

If using LVPECL in Spartan-6 device then you should apply the following constraint to your UCF file:


AR# 34635
Date Created 04/05/2010
Last Updated 10/22/2014
Status Active
Type Error Message
  • ISE - 10.1
  • ISE Design Suite - 11.1
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