Error CMP412: The external feedback pin of PLL <pin name>, must have a fanout of 1.

The external feedback (EXTFB) of any PLL core is hardwired to an external PAD. It can only be driven by a regular I/O in the design. The net connecting the regular input I/O core to the PLL external feedback must have a fanout of 1.

Action

Make sure to drive the external feedback of any PLL core with a regular I/O core with a fanout of 1.