When running TRACE, the following warning occurs:
WARNING:ConstraintSystem:12 - In file: <...>.ucf: Loading a 'MaxSkew' constraint from a UCF file is not supported at this time. This constraint specification will be ignored.
In the timing analysis report file, this constraint is still analyzed.
Why does the warning occur?
Since ISE 8.2i, a new plugin version of the Timing Analyzer exists for Virtex-5 devices. This allows clicking on a constraint in the report file and editing this in the Constraints Editor.
In this version, the 'MaxSkew' constraint is not yet supported for this feature and therefore the warning occurs.
The warning can also occur for other devices, even though the new plugin version is not yet supported for them. It can be ignored.