4. Modbus communication
The Modbus variant used in GMW87 is Modbus RTU. For a list of the Modbus registers available
in GMW87, see
You can use up to 8 transmitters on the same RS-485 line. You must configure each transmitter
on the line to have a different Modbus address.
Before taking the transmitter into use, check that the Modbus device address, bit
rate setting, and parity setting match the settings in your system.
The number of stop bits is not significant. The device supports automatically both
1 and 2 stop bits.
3
D
RS
D
GND
VS
VS
1
2
5
6
4
Figure 28 GMW87 component board with DIP switches and screw terminals
1
DIP switches for setting the GMW87 Modbus device address
2
DIP switches for selecting Modbus communication bit rate and parity (N/E)
3
Screw terminal not used in GMW87
4
DIP switch for 120 Ω RS-485 bus termination. Switch RS-485 bus termination
ON
only on
the last device of the wiring if there is no separate terminator on the bus.
5
RS-485 (Modbus) screw terminals
6
Power supply input (18 … 35 VDC or 20 … 30 VAC) screw terminals
GMW80 Series User Guide
M211748EN-G
34
