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333 15 ControlLogix Controllers Programmable logic controllers continue to evolve as new technologies are added to their capabilities. The PLC started out as a replacement for banks of relays used to turn outputs on and off as well as for timing and counting functions. Gradually, various math and logic manipulation functions were added. In order to serve today’s expanding industrial control system needs, leading automation companies have created a new class of industrial controllers called programmable automation controllers or PACs (Figure 15-1). They look like PLCs in their physical appearance but incorporate advanced control of communication, data logging, and signal processing, motion, process control, and machine vision in a single programming environment. The Allen-Bradley programmable automation controller family includes the ControlLogix system, CompactLogix system, FlexLogix system, SoftLogix 5800 controller, and DriveLogix system. Software is the essential difference between PACs and PLCs. Basically, the ladder logic configuration does not change but the addressing of the instructions changes. Application of the software that pertains to the Logix control platform of controllers will be covered in the various sections of this chapter. Knowledge of basic ladder logic instructions and functions (bit, timer, counter, etc.) covered in previous chapters of the text is assumed and is thus not repeated in this chapter. Figure 15-1  Programmable automation controllers (PACs). Source: Image Courtesy of Rockwell Automation, Inc.


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