... first PLCs were developed and why they were better than the existing control methods ” the difference between the open frame, shoebox, and modular PLC configurations, and the advantages and disadvantages ... loops and optional programming commands The processor consists of the microprocessor, system memory, serial communication ports for printer, PLC LAN link and external programming device and, in ... fundamental understanding of the various types of PLCs available, the advantages and disadvantages of each, and the way in which a PLC executes a program The open frame, shoebox, and modular PLCs are each...