![]() ![]() ![]() and a code specifying the exception ( Exception Code, 1 byte)įigure 3 presents a visualization of these packages.the function code corresponding to the request + 0x80 (128), ( Error Code, 1 byte).and response specific data ( Response Data, varying number of bytes).the function code corresponding to the request ( Function Code, 1 byte).and function specific data ( Function Data, varying number of bytes).a code specifying a function ( Function Code, 1 byte).The protocol specification defines three types of PDU's: The stateless communication is based on a simple package, that is called Protocol Data Unit (PDU). To prevent confusion, the following directed relations describe Master-Slave in terms of the Client-Server paradigm:Ī transaction and it's context is visualized in Figure 2. In the field where this protocol is usually applied, there exists a concept that is one of the possible schemas governing the lower level communication behavior on a network using a shared signal cable: Master-Slave. much like HTTP), based on transactions, which consist of a request (issued by the client) and a response (issued by the server). Basically Modbus is an application layer protocol (see Figure 1) for communication between devices, mainly to exchange data typical for the field of automation.Īt this level Modbus is a stateless client-server protocol (e.g. ![]()
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