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AR# 14865

5.1i Constraints Editor - Adding a period constraint causes "ERROR: XdmHelpers:664 - Period specification..."


General Description:

When I fit a CPLD design with a PERIOD constraint on a TNM group, the following error is reported:

"ERROR: XdmHelpers:664 - Period specification "TS_CLK" references the TNM group "CLK", which contains only pad elements. Only synchronous elements are permitted in a period specification. If this group was intended to reference the synchronous elements driven by the pad(s), you may need to change the TNM property to a TNM_NET property, so that it will be traced forward from the pad(s)."


To work around this issue, change the group constraint from a TNM to a TNM_NET.

This problem is fixed in the latest 5.1i Service Pack, available at:


The first service pack containing the fix is 5.1i Service Pack 1.

AR# 14865
Date Created 08/29/2007
Last Updated 01/18/2010
Status Archive
Type General Article