Wiring Rs485 Interface; Figure 2.2 Multi-Point, Half-Duplex Rs485 Wiring; Table 2.3 Half Duplex Hookup - Omega C4EIT User Manual

2.3.1 Wiring Master/Slave Units via RS485 Interface
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 2.3 shows multi-point, half-duplex RS485 interface connections for the iServer.
Value of the termination resistor is not critical and depends on the cable
impedance.
Table 2.3 shows RS485 half-duplex hookup between the iServer serial port and device
with RS485 communication interface.

Table 2.3 Half Duplex Hookup

Pin#
Pin 9 +Tx/+Rx (+Transmit/+Receive)
Pin 10 -Tx/-Rx (-Transmit/-Receive)
Pin 8

Figure 2.2 Multi-point, Half-Duplex RS485 Wiring

iSeries
RTN (Common GND)
DEVICE # WITH RS485
+Tx/+Rx (+Transmit/+Receive)
-Tx/-Rx (-Transmit/-Receive)
GND (Common GND)
6