Modbus is a communication protocol, but attention should be paid to its transmission limitations.
Firstly, the Modbus protocol uses different physical layers (such as RS-232, RS-485), each with different transmission rates and distance limitations. Therefore, when using the Modbus protocol, it is necessary to consider the characteristics of the physical layer to ensure the correct transmission of messages.
Secondly, the Modbus protocol also has limitations on data size. The Modbus RTU protocol supports data transmission of up to 256 bytes per packet, while the Modbus TCP protocol supports data transmission of up to 65535 bytes per packet. If larger data needs to be transmitted, it can be divided into multiple message frames for transmission.
In addition, since the Modbus protocol is based on a master-slave structure, the address of each slave device also needs to be restricted. In the Modbus RTU protocol, the address of each slave device must be an integer between 1 and 247, while in the Modbus TCP protocol, each slave device is identified using an IP address and port number.
Finally, it is important to note the security limitations of the Modbus protocol. The Modbus protocol does not provide any security protection mechanisms, so other security measures are needed to protect data security during communication.
Leave a Reply