Omega C4EIT/-EIT Wiring Master/Slave Units via RS485 Interface, Half Duplex Hookup Pin# ISeries

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.

Figure 2.2 Multi-point, Half-Duplex RS485 Wiring

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#	iSeries	DEVICE # WITH RS485
Pin 9	+Tx/+Rx (+Transmit/+Receive)	+Tx/+Rx (+Transmit/+Receive)
Pin 10	-Tx/-Rx (-Transmit/-Receive)	-Tx/-Rx (-Transmit/-Receive)
Pin 8	RTN (Common GND)	GND (Common GND)

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