Advantech SOM-5786 Manual de usuario descargar pdf (Pagina 19)

11 Chapter 2

2.2.5 Terminal Resistor Setup for RS-422/485

The onboard termination resistor (120 Ohm) for COM1/COM2 can be

used for long distance transmission or device matching (Default Open).

Each terminal resistor responds to different channels for RS-422/485.

Usually, these resistors are needed for both ends of the communication

wires and the value of the resistors should match the characteristic imped-

ance of the wires used.

Table 2.1: Terminal Resistor Settings

COM Port Switch No. Pin Setting Description

COM1 SW4 1 ON 120 Ohm between Data+/

Data- (RS-485)

Or 120 Ohm between Tx+/Tx-

(RS-422)

OFF Open (Default)

2 ON 120 Ohm between Rx+/Rx-

(RS-422)

OFF Open (Default)

COM2 SW5 1 ON 120 Ohm between Data+/

Data- (RS-485)

Or 120 Ohm between Tx+/Tx-

(RS-422)

OFF Open (Default)

2 ON 120 Ohm between Rx+/Rx-

(RS-422)

OFF Open (Default)

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