Rs-485 And Rs-422 Tip; Application Port(S) - ProSoft Technology MVI69-GSC CompactLogix User Manual

MVI69-GSC ♦ CompactLogix or MicroLogix Platform
Generic ASCII Serial Communication Module
5.3.3 RS-422
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:
5.3.4 RS-485 Application Port(s)
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: Terminating resistors are generally not required on the RS-485 network, unless you are experiencing
communication problems that can be attributed to signal echoes or reflections. In these cases, installing a
120-ohm terminating resistor between pins 1 and 8 on the module connector end of the RS-485 line may
improve communication quality.

RS-485 and RS-422 Tip

If communication in the RS-422 or RS-485 mode does not work at first, despite all
attempts, try switching termination polarities. Some manufacturers interpret + and -, or A
and B, polarities differently.
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