Below are some commonly used function codes. The Modbus protocol defines multiple function codes for accessing and manipulating memory areas. Taking Modbus TCP as an example, its message structure includes MBAP(Modbus Application Protocol Header)+PDU(Protocol Data Unit). It is important to choose the appropriate storage area for reading and writing operations according to the application scenario. Storage Area NameĮach storage area has its own address range and read/write operation code. Different types of storage areas correspond to different read-write operations. The Modbus protocol defines four types of storage areas: Coils, Discrete Inputs, Input Registers, and Holding Registers. It facilitates data exchange between devices and enables the transmission of control commands, allowing different devices to coordinate with each other. It is mainly used for monitoring and controlling automation equipment such as sensors, motors, and PLCs.
Modbus adopts a master-slave mode and supports multiple transmission modes, including serial (RS-232/485) and Ethernet versions (TCP/IP). Originally developed by Modicon in 1979, it has evolved into one of the universal communication standards widely used in industrial automation scenarios. Modbus is a serial communication protocol used to connect industrial automation devices.
