It is recommended that you use the Assign Alarm command rather than create a custom alarm when you add an alarm to a module that uses the PID, FLC, RTO, ALM, AI, and DI function blocks. To access the Assign Alarm command, select and right-click the function block. Alarms created with the Assign Alarm command are pre-configured with the alarm parameter, the limit parameter, and the two message variables %P1 and %P2, as well as the alarm priority and type. Custom alarms require you to manually define all these parameters, except for the limit parameter, which is not available. Custom alarms are typically used for conditions not addressed by the default block alarms.