Rockwell-automation 1771-DB Basic Module User Manual - Series A Manuale Utente Scaricare il pdf (Pagina 36)

Using the Serial Ports

Chapter 4

4–12

Figure

4.9

Point-to-Point RS-422 Connections

Figure 4.10

Multi-drop configuration with master and multiple slaves

Important: When you use the peripheral port as a 422 port, you must

connect pin 4 to pin 5 on the port.

When using an RS-422 interface you must install termination resistors at

each end of the line. The module has a jumper selectable termination

resistor (Refer to figure 3.2). Use a cable with 2 twisted pairs and a

nominal impedance of 100 ohms.

Important: Use terminating resistors only at the ends of the link if using

multiple RS-422 devices, and at both ends if using point-to-point

connections.

4.4.5

Connecting

RS-422 Devices

(continued)

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Rockwell-automation 1771-DB Basic Module User Manual - Series A Manuale Utente Pagina 36