The role and characteristics of modbus gateway

What is a Modbus gateway What is the role of a Modbus gateway

　　 Modbus gateway can be called Ethernet communication gateway, it can realize the conversion between Modbus RTU/ASCII and Modbus TCP protocol. The Modbus protocol is divided into two types, one is Modbus RTU (or ASCII) based on RS485, and the other is Modbus TCP based on Ethernet. Modbus gateway is a converter that converts Modubs RTU device data into Modbus TCP data. Due to the limitation of RS485 bus, Modbus TCP has the following advantages compared with RTU:

(1) The existing Ethernet network can be used, eliminating the need for RS485 wiring.

(2) It can support multiple hosts to access Modbus instruments at the same time.

　　The role of modbus gateway:

　　 Modbus gateway is a network hub communication protocol conversion device of industrial automation system. It connects with smart meters, collects data from lower meters to modbus gateway, connects with computer network, and communicates with network computers according to Modbus Tcp protocol.

There are two types of Modbus gateways: storage type and common type. Compared with ordinary Modbus, storage type Modbus can save the contents of the read registers inside the gateway, so that the speed of Modbus TCP query can be greatly improved, and the performance of multi-host access is supported. More superior. 

　　 Modbus has the following characteristics:

　　 1. Standard and open, users can use Modbus protocol for free and with confidence, without paying license fees, and will not infringe on intellectual property rights. Currently, there are more than 400 manufacturers supporting Modbus and more than 600 products supporting Modbus.

　　2, Modbus can support a variety of electrical interfaces, such as RS-232, RS-485, etc., and can also be transmitted on various media, such as twisted pair, optical fiber, wireless, etc.

　　3, Modbus frame format is simple, compact and easy to understand. It is easy for users to use and easy for manufacturers to develop.

　　Modbus register type description

　　1— Coil status: output port, the output status of the port can be set, and the output status of this bit can also be read;

　　2— Discrete input state: input port, change the input state through external settings, readable but not writable;

　　3— Holding register: certain parameters set when the controller is running, readable and writable;

　　4— Input register: some parameters obtained from external equipment when the controller is running, readable but not writable;