Error CMP407: DDR instance <DDR_instance_name> cannot drive pin <pin_name> (tristate enable).

The built-in I/O DDR functions can only be used on the input or the output path of an I/O macro.  

Action

If you need the DDR functionality on the I/O tristate enable path, use regular gates to build the DDR functionality. This may have performance and area implications and Actel does not recommend it.