Description

When I attempt to select my input clock in Constraints Editor, all I see is the clock that comes out of my ISERDES.  

Why am I unable to see my input clock in the clock list?

Solution

The Constraints Editor is not tracing back to the input clock and is only referencing the clock that comes out of the ISERDES component.  

This issue should be fixed in the next major release. 

To work around this issue, manually add the constraints to the UCF.