Modbus Communication Principle - 3onedata GW11 Series User Manual

Slave state diagram is as follows:

11.3 Modbus communication principle

Modbus protocol is a client / server application layer protocol, the communication
process follows the following process:
The client sends a request to the server。

The server analyzes and processes the client requests，and sends the results to

the client.
If an error occurs, the server will return an exception code to the client

The client sends additional information to the message data field sent by the server to
the server device, and the server uses this information to perform the operation of the
function code definied. If there is no error associated with requesting the Modbus
function in a correctly received Modbus ADU, the response data sent by the server to
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(I)GW11XX Modbus User Manual
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