Error CMP410: I/O instance <I/O_instance_name> has fanout more than 1. It cannot be combined with the DDR instance <DDR_instance_name>.

The DDR_REG core is intended to be paired with a regular input I/O core. To use the built-in input DDR I/O function the net connecting the DDR_REG macro to the regular input I/O macro must have a fanout of 1.

Action

Make sure to connect this DDR_REG core to only one regular input I/O macro.