Logix operating cycle

The entire Logix family of controllers (ControlLogix and CompactLogix) has diverged from traditional synchronous PLC scan architecture in favor of a more efficient asynchronous operation. Like most modern computer systems, asynchronous operation allows the Logix controller to handle multiple tasks at the same time by slicing the processing time between each tasks. The continuous updating of information in an asynchronous processor creates some programming challenges, which we will address throughout the book. The following diagram illustrates the difference between the synchronous and asynchronous operation: