Sending data to, from and between embedded controllers. A common problem in industrial applications is retaining mission-critical data during power outages or other emergencies. To understand how an embedded controller handles outages, one needs to know the nature of “interrupts.”

When a controller’s microprocessor recognizes an interrupt, the microprocessor almost immediately shelves what it is doing and jumps to the appropriate interrupt service routine.

Software engineers use this built-in, very fast hardware and software facility in three ways:

• To respond quickly to unscheduled or anomalous events.
• To acknowledge some input, but defer its processing until later.
• To respond to interrupts generated by some regular timing mechanism to achieve the regulated,orderly operation of some sequence.