This chapter first introduces an overview of existing PLC systems, then proposes the overall architectural design of the general-purpose industrial controller designed in this paper, analyzes the functions to be implemented in hardware and software, and finally analyzes the functions of each part and proposes specific implementation schemes.

2.1 Introduction to PLC Systems

A Programmable Logic Controller (PLC) is a new type of general-purpose automatic control device [14] based on microprocessors, developed by integrating computer technology, automatic control technology, and communication technology. It uses a type of programmable memory for internally storing programs, executing user-oriented instructions such as logical operations, sequential control, timing, counting, and arithmetic operations, and controls various types of machinery or production processes through digital or analog input/output. It is a core component of industrial control [15].

Siemens S7-200 series PLCs are integral PLCs. Figure 2-4 shows the internal block diagram of one such PLC basic unit. Its