The PLC surface grinder sequential scanning method is simple and intuitive, which simplifies the program design and provides a strong guarantee for the reliable operation of the PLC.

The cyclic scanning process of the user program can be divided into three stages: input sampling, program execution, and output refresh.
1. Input sampling stage
The PLC surface grinder manufacturer tells you that PLC reads and stores the signal status of all input interfaces through the input interface and stores it in the input image register, that is, refreshes the original state of all input signals. The PLC surface grinder manufacturer tells you to continue to the program execution stage, even if the input state changes at this time, the content of the input image register will not change. The change of input state can only be re-read in the input sampling phase of the next working cycle.
2. Program execution stage
The PLC surface grinder scans the user program, scans the user program one by one according to the state of the input signal in this cycle and the state of the output signal in the previous cycle, performs corresponding logic or arithmetic operations, and stores the result of the operation in a special register. If the program output instruction is executed, the corresponding operation result is stored in the output image register.
3. Output refresh stage
The PLC surface grinder manufacturer tells you that after all instructions are executed, the state in the output image register is the state to be output, and it is dumped into the output buffer during the output refresh phase, and then the output points of the refreshed output buffer are transferred. The status of all is sent to the output terminal of the PLC through the output interface circuit, which is the actual output of the PLC.
The PLC surface grinder manufacturer tells you that this working method is called the scanning method. The time it takes for the above three steps to execute one cycle is called the scan cycle. The PLC scan period is one of the important parameters of the PLC, which reflects the sensitivity or hysteresis of the PLC to the input signal.