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13
Chapter 2
2.4 Terminal Resistor Setup for RS-422/485
The onboard termination resistor (120 Ohm) for COM1-6, COM A,
and COM B can be used for long distance transmission or device match-
ing (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.
Terminal Resistor Settings
COM Port Switch Pin
Setting
Description
COM 1,2
SW 11 1 (COM1) ON
120 Ohm between Data+/
Data-
OFF
Open (Default)
2 (COM2) ON
120 Ohm between Data+/
Data-
OFF
Open (Default)
COM A
COM B
SW 10
SW 9
1
ON
120 Ohm between Data+/
Data- (RS-485 COM A, B
only)
Or 120 Ohm between Tx+/
Tx-
(RS-422)
OFF
Open (Default)
2
ON
120 Ohm between Rx+/Rx-
(RS-422)
OFF
Open (Default)
COM 3
COM 4
COM 5
COM 6
SW 6
1 (COM3) ON
120 Ohm between Data+/
Data-
2 (COM4)
3 (COM5) OFF
Open (Default)
4 (COM6)
Содержание UNO-2174A
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Страница 35: ...Appendix A System Settings and Pin Assignments ...