Communication Using Modbus Rtu - Siemens SINAMICS G110M Function Manual

5.4

Communication using Modbus RTU

Overview of communication using Modbus
The Modbus protocol is a communication protocol based on a client/server architecture.
Selected parameters and process data are exchanged in a cyclic access via the Modbus
register.
Modbus offers three transmission modes:
● Modbus ASCII - via a serial interface
data in the ASCII code. The data throughput is lower compared to RTU.
● Modbus RTU - via a serial interface
data in the binary format. The data throughput is greater than in ASCII code.
● Modbus TCP - via Ethernet
Data are transferred as TCP/IP packages TCP port 502 is reserved for Modbus TCP.
SINAMICS G120 inverters support Modbus RTU.
General information about communication using Modbus RTU
Communication using Modbus RTU takes place over the RS485 interface with a maximum of
247 slaves.
● The maximum cable length is 1200 m.
● To polarize the receive and transmit lines, there are two 100 kΩ resistors, which you can
switch in or switch out using the DIP switch next to the fieldbus interface.
Note
It is not permitted to change over the units
The "Unit switchover" function – for details see the operating instructions of the Control Unit
– is not permissible with this bus system!
Fieldbuses
Function Manual, 04/2018, FW V4.7 SP10, A5E34229197B AE
Communication via RS485
5.4 Communication using Modbus RTU
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