Condair LINKS Series - 4 Modbus RTU; Before Installation; Network Structure Modbus RTU

9Modbus RTU
4 Modbus RTU
4.1 Before installation
To do installation works on the respective device you have to switch off the device and secure it from
unintended switch-on according to the operation manual! Also follow any other safety instructions from
the user manual. If not mentioned otherwise, the specications of the Modbus RTU or RS485 standard
apply. The installation has to be carried out in accordance with local regulations.
It's recommended to update the device software to the newest version before start the implementation
of the device in a Modbus RTU network.
The respective device acts as a slave only. The Modbus RTU master - slave principle only allows the
master (e.g. a control computer) to initiate date transmission. The respective slave device then reacts and
exports the requested data to the master or carries out the action required by the master. In a Modbus
RTU network only one master may be present.
4.2 Network structure Modbus RTU
GND
+
–
GND
+
–
J6
GND
+
–
J6
Device 1
Master
RS485
Device 2
Shield
Fig. 1: Example Modbus RTU Network
– Connect the cable shield on one side with the functional earth
– Connect all GND together
– Install bus line separate from supply voltage
– Topology: Daisy chain
– All devices of the same network need the same settings concerning baud rate and parity
– Every Modbus device address can only be allocated once within the same network.