When I create a Timespec PERIOD within PlanAhead, incorrect syntax is used which causes Constraint System errors similar to the following.
"ERROR:ConstraintSystem - In file: floorplan_1.ucf(9): Constraint 'PERIOD' was
applied to 'RISING FFS', but is only applicable to the following:
design:NET or constraint:timegrp or global:clocknets
Please see the Constraints Guide for more information on this constraint."
This will be fixed in a future release of PlanAhead.
To create Timespec PERIOD constraints using predefined groups in the current release, use Constraints Editor.