pvd coating machine PLC usually consists of central processing unit, memory, input and output (I/O) channels, timer (T), counter (C) and other units. Sometimes external devices such as printers and CRT monitors are also connected, and the control program is input by the programmer. The structure of the PLC is similar to that of a computer, and the functions of each component are:

①The central processing unit CPU of the pvd coating machine. It is the core component of the PLC. It is composed of a processor, an intermediate variable memory, etc., and is similar to the CPU of a microcomputer. Its function is to receive and store the user program and data input from the programmer according to the function given by the system program in the PLC; receive the status and data of the on-site input device by scanning, and store them in the data register; diagnose power supply, PLC internal circuit Syntax errors during working status and programming. When the PLC is running, read the user program one by one from the memory, and generate corresponding signals according to the tasks specified by the program to turn on and off the relevant circuits; perform data access, transmission, combination, and comparison in time-sharing and channel-sharing and transformation, complete the logic control or calculation tasks specified in the user program; update the status of the relevant flag bits or the relevant content in the data register according to the calculation results, and realize output control, tabulation and data communication, etc.
②pvd coating machine program memory. Among them, the system program memory is used to store the system engineering program (monitoring program), function subroutine and management program. The user program memory is used to store the control algorithm coefficient (analog quantity) and the program compiled by the user. The PLC user memory usually expresses the capacity of the memory in units of words (16 bits/word). The memory type and capacity given in the PLC product information refer to the user memory. Since the user memory is powered by lithium batteries, the programs in the user memory will not be lost even if the power grid fails.
③ pvd coating machine input and output channel I/O. I/O is the connecting part between CPU and on-site vacuum device or other external equipment. PLC provides I/O with various purposes, various operating levels and driving capabilities for users to choose. I/O has level shifting, electrical isolation, serial exchange, data transmission, error checking, A/D or D/A conversion and other functional controls.