Wiring - ProSoft Technology CompactLogix MVI69E-MBS User Manual

MVI69E-MBS ♦ CompactLogix™ Platform
Modbus Serial Enhanced Communication Module
8.6.2 RS-422 Wiring
The RS-422 interface requires a single four or five wire cable. The Common connection
is optional, depending on the RS-422 network devices used. The cable required for this
interface is shown below:
8.6.3 RS-485 Wiring
The RS-485 interface requires a single two or three wire cable. The Common connection
is optional, depending on the RS-485 network devices used. The cable required for this
interface is shown below:
Note: This type of connection is commonly called a RS-485 half-duplex, 2-wire connection. If you have RS-
485 4-wire, full-duplex devices, they can be connected to the gateway's serial ports by wiring together the
TxD+ and RxD+ from the two pins of the full-duplex device to Pin 1 on the gateway and wiring together the
TxD- and RxD- from the two pins of the full-duplex device to Pin 8 on the gateway. As an alternative, you
could try setting the gateway to use the RS-422 interface and connect the full-duplex device according to
the RS-422 wiring diagram. For additional assistance, please contact ProSoft Technical Support.
Note: Depending upon devices on the network, if there are problems in RS-485 communication that can be
attributed to the signal echoes or reflections, then consider adding 120 OHM terminating resistors at both
ends of the RS-485 line.
ProSoft Technology, Inc.
Reference
User Manual
Page 157 of 159