UNO-1170A/AE User Manual 12
2.3.5 Terminal Resistor Setup for RS-422/485 SW3
The onboard termination resistor (120 Ohm) for COM3 can be used for
long distance transmission or device matching. (Default Open.) Each ter-
minal 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.
SW3 Pin 3,4 is reserved for on board COM port pin header use only.
Table 2.3: Terminal Resistor Settings
COM port Switch No. Pin Setting Description
COM3 SW3 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)
