描述

General Description: If the NGD that has a PERIOD defined, but the

UCF doesn't, it can not be deleted or changed in the Constraint Editor.

If a new PERIOD constraint is created in CE the group is added to

the ucf but not the new PERIOD Timespec.

解决方案

To resolve this issue open the UCF file in a text editor and add the desired

constraint. For Example:

TIMESPEC "TS_CLK" = PERIOD "CLK" 20 ns;