ModBus is a communication protocol used to connect automation equipment (such as PLCs, temperature controllers, etc.) and computers. The Modbus protocol is widely used in industrial control systems and supports a variety of communication methods, including ModBus RTU, ModBus ASCII and ModBus TCP. This article will explain the differences and application scenarios of these three communication methods.Digital RadioModbus protocolModBus RTU (Remote Terminal Unit) is the most common implementation of the ModBus protocol. It uses binary data transmission and has high transmission efficiency and stability. It uses serial communication and supports both RS232 and RS485 interfaces. In RTU mode, two hexadecimal characters can be transmitted per byte. For example, 0xAB will be sent directly as hexadecimal 0xAB (binary 10101011).Communication protocolIts message frame format consists of the following parts:ModBus RTU protocolModBus ASCII (American Standard Code for Information Interchange) uses ASCII code to transmit text information. Compared with ModBus RTU, its transmission efficiency is lower, but it has better readability. ModBus ASCII also uses serial communication and supports two interfaces, RS232 and RS485, suitable for short-distance communication. In ASCII mode, each 8-bit byte is divided into two ASCII characters for transmission, and the message frame starts with an English colon ":" and ends with a carriage return and line feed (CRLF) symbol. For example, the hexadecimal number 0xAB will be decomposed into ASCII characters "A" and "B" for transmission.
