Owner's manual

2.4.4 Wiring RS485 Interface -- DIN Rail iServer
RS485 interface uses a two-wire communication system (one for transmitting and one for
receiving) plus a common wire to connect to the shield of the cable. It is recommended
to use a shielded cable with one twisted pair.
Use of twisted pair and shield will significantly improve noise immunity.
Figure 2.7 shows multi-point, half-duplex RS485 interface connections for the iServer.
Figure 2.7 Multi-point, Half-Duplex RS485 Wiring - DIN Rail iServer
Value of the termination resistor is not critical and depends on the cable impedance.
Table 2.6 shows RS485 half-duplex hookup between the iServer serial port and device
with RS485 communication interface.
Table 2.6
Pin# iServer DEVICE WITH RS485
3
+Tx/+Rx (+Transmit/+Receive) +Tx/+Rx (+Transmit/+Receive)
4 -Tx/-Rx (-Transmit/-Receive) -Tx/-Rx (-Transmit/-Receive)
2
RTN (Common GND) GND (Common GND)
DEVICE #1
DEVICE #29
DEVICE #31
DEVICE #30
DEVICE #2
iServer
120 Ohm
Termination resistor
120 Ohm
Termination resistor
GND
-Tx/-Rx
+Tx/+Rx
+Tx/+Rx
-Tx/-Rx
Twisted shielded pair
-Tx/-Rx
-Tx/-Rx-Tx/-Rx
-Tx/-Rx
+Tx/+Rx
+Tx/+Rx
GND
GND
GND
GND
+Tx/+Rx
+Tx/+Rx
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COMMUNICATIONS
ETHERNET
DC POWER IN
RX TX LINK ACT
RESET
+ - N/C
11