The internal working mode of the PLC generally adopts the cyclic scanning working mode, and the interrupt working mode is added to some large and medium-sized PLCs. When the user finishes debugging the user program, write the program into the PLC memory through the programmer, and connect the field input signal and the controlled actuator to the input end of the input module and the output end of the output module accordingly, and then Select the PLC work mode as the run work mode, and the subsequent work will be completed by the PLC according to the user program. The overview diagram is the PLC execution process block diagram. In the working process of PLC, it mainly completes the processing of six modules.

PLC hardware configuration

Power components

The power supply component is used to provide the power required for the operation of the PLC, and can convert the external power supply into a power supply suitable for the inside and the case of the PLC.

2. Microprocessor CPU and memory components

The microprocessor CPU is the core device of the PLC. The CPU varies from manufacturer to manufacturer. Some use standard chips sold in the market and some use programmable controller dedicated chips.

There are two types of memory components: ROM and RAM.

3. Input and output components

The input and output components are the interface between the PLC and the industrial production site to exchange data. Unlike ordinary computers, the PLC's working environment is relatively poor and requires strong anti-interference ability. The input and output components are designed for this.