Prosoft-technology MVI46-MCM Manuel d'utilisateur télécharger pdf (Page 79)

MVI46-MCM ♦ SLC Platform Reference

Modbus Communication Module User Manual

ProSoft Technology, Inc. Page 79 of 108

March 29, 2011

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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Prosoft-technology MVI46-MCM Manuel d'utilisateur Page 79