储执行逻辑运算、顺序控制、 定时、 计数和运算等操作的指令;并通过数字输入和输出操作，来控制各类机械或生产过程。用户编制的控制
程序表达了生产过程的工艺要求，并事先存入PLC控制器的用户程序存储器中。运行时按存储程序的内容逐条执行，以完成工艺流程要求的
操作。PLC控制器的CPU内有指示程序步存储的程序计数器，在程序运行过程中，每执行-步该计数器自动加1, 程序从起始步(步序号为
零)起依次执行到终步(通常为END指令)，然后再返回起始步循环运算。PLC控制器每完成- -次循环操作所需的时间称为-个扫描周期。不同
型号的PLC控制器，循环扫描周期在1微秒到几十微秒之间。PLC用梯形图编程,在解算逻辑方面，表现出速的优点，在微秒量级，解算1K
逻辑程序不到1毫秒。它把所有的输入都当成开关量来处理，16位(也有32位的)为一 个模拟量。 大型PLC控制器使用另外一个CPU来完成模
拟量的运算。把计算结果送给PLC的控制器。
PLC controller is developed by imitating the original relay control principle. In the 1970s, PLC controller only has switching logic control, * which is applied in the automobile manufacturing industry. It is stored by
Store instructions for performing logical operations, sequence control, timing, counting and operations; And through digital input and output operation, to control all kinds of machinery or production process. Control of user headcount
The program expresses the technological requirements of the production process and is stored in the user program memory of the PLC controller in advance. When running, it shall be executed item by item according to the contents of the stored program to complete the process flow requirements
Operation. There is a program counter in the CPU of the PLC controller that indicates the stored program steps. In the process of program operation, the counter will automatically increase by 1 for each execution step, and the program will start from the starting step (step number is
From zero) to the final step (usually the end instruction), and then return to the starting step cyclic operation. The time required for the PLC controller to complete each cycle operation is called a scanning cycle. Different
Model PLC controller, the cycle scanning cycle is between 1 microsecond and dozens of microseconds. PLC is programmed with ladder diagram, which shows the advantage of speed in solving logic. In the order of microseconds, it solves 1K
The logic program takes less than 1 millisecond. It treats all inputs as switching values, and 16 bits (also 32 bits) are an analog value. The large PLC controller uses another CPU to complete the module
Operation of quasi quantity. Send the calculation results to the PLC controller.
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