The PLC of pvd coating machine is usually composed of central processing unit, memory, input/output (I/O) channel, timer (T), counter (C), and other units. Sometimes external devices such as printers and CRT displays are also connected, and the control program is input by a programmer. The structure of PLC is similar to that of a computer, and the functions of each component are:
① The central processing unit (CPU) of the pvd coating machine is the core component of the PLC, consisting of a processor, intermediate variable memory, etc., similar to the CPU of a microcomputer. Its function is to receive and store user programs and data input from the programmer according to the functions assigned by the system program in the PLC; Receive the status and data of the on-site input device through scanning and store them in the data register; Diagnose power supply, PLC internal circuit working status and Syntax error during programming. During PLC operation, read user programs one by one from the memory and generate corresponding signals according to the tasks specified by the program to open and close related circuits; Perform data access, transmission, combination, comparison, and transformation in different time and channels, and complete tasks such as logical control or computation specified in user programs; Based on the calculation results, update the status of the relevant flag bits or the relevant content in the data register to achieve output control, tabulation, and data communication.
②
pvd coating machine program memory. The system program memory is used to store system engineering programs (monitoring programs), functional subroutines, and management programs. The user program memory is used to store control algorithm coefficients (analog quantities) and user generated programs. PLC user memory is usually represented in words (16 bits per word) to represent the capacity of the memory. The memory type and capacity given in the PLC product documentation refer to user memory. Due to the use of backup lithium batteries for power supply in the user memory, even if the power grid is cut off, the programs in the user memory will not be lost.
③ The input/output channel I/O.I/O of the pvd coating machine is a connecting component between the CPU and the on-site vacuum device or other external devices. PLC provides I/O for various purposes, operating levels, and driving capabilities for users to choose from. I/O has the functions of level transfer, Galvanic isolation, serial pie line exchange, data transmission, error code verification, A/D or D/A conversion and other control functions.
