Modbus Tcp - Siemens SIRIUS 3RW5 Equipment Manual

Description
3.3 Functions of the 3RW5 Modbus communication module
3.3 Functions of the 3RW5 Modbus communication module
3.3.1

Modbus TCP

Modbus TCP is a bus system according to the standard IEC 61784-2 CPF 15/1 with the
transmission protocol Modbus. Modbus TCP is based on a client/server architecture.
As the client, the controller has the initiative in data transmission and transmits requests to
the server. The requests contain the Function Code and additional data. A server cannot
transmit information to the client autonomously. The 3RW5 soft starter works as the server
and can only respond to the requests of the client. The 3RW5 soft starter supplies the
relevant feedback messages to the bits and registers retrieved by the client or takes over the
bits and registers written by the client into the internal memory. No requests can be
transferred from server to server.
The server processes the requests of the client and answers within a certain time with one of
the following acknowledgments:
● Requested data
● Error code (Exception Code)
You can find more information about the telegram structure in chapter Telegram structure
Modbus TCP (Page 28).
24
SIRIUS 3RW5 Modbus communication module
Equipment Manual, 03/2020, A5E43676481002A/RS-AC/003