Scheduled communications are REPEATED on a regular pre-configured cycle, and include those messages carrying measurements or outputs used for control PURPOSES.

Unscheduled communications are fitted into IDLE times in the scheduled message cycle, and are used for almost everything ELSE: OPERATOR display updates, tuning parameter and mode changes, process alarms, trend reports, configuration changes, diagnostics, time distribution. (Unscheduled messages can be prioritised; for example, alarms can be dealt with urgently.)

Scheduled communications are repeated on a regular pre-configured cycle, and include those messages carrying measurements or outputs used for control purposes.

Unscheduled communications are fitted into idle times in the scheduled message cycle, and are used for almost everything else: operator display updates, tuning parameter and mode changes, process alarms, trend reports, configuration changes, diagnostics, time distribution. (Unscheduled messages can be prioritised; for example, alarms can be dealt with urgently.)