ID:15655 Port <text> of Clock Control Block "<name>" can't drive <text> port of Clock Control Block "<name>"

CAUSE: The specified output port of the specified Clock Control Block cannot drive the specified port of the specified Clock Control Block. The specified output port of the specified Clock Control Block cannot drive the ports of another Clock Control Block. If you get this error during fitting, it means the Fitter could not merge all Clock Control Blocks in a legal way.

ACTION: Modify the design so that specified Clock Control Block does not drive another Clock Control Block.