Jumper Settings for RS-422 or RS-485
Inside the unit, there is one 3-pin DIP switch which is set to select the mode of operation. You need to open the case then you can set the switch settings to RS-422 mode, or RS-485 mode, as per the requirements of your application. After setting of switches, you then proceed to insert the driver CD and start driver installation.
The RS-422 & RS-485 Mode Block Configuration Settings are listed as follows.
Operation Mode | S1 | S2 | S3 | |
RS-422 | 4 wire with Handshaking | ON | ON | ON |
RS-485 | Full Duplex (4 wire) | OFF |
ON | ON |
Half Duplex (2 wire) with Echo | OFF |
OFF |
ON | |
Half Duplex (2 wire) - without Echo | OFF |
OFF |
OFF |
Example jumper block setting ( RS-422 mode )
Inside the unit, there is one 3 x 7 (21 pin) header blocks which are jumpered to enable Tx, Rx, CTS 120 Ohm termination resistors and Tx, Rx 750 Ohm BIASing resistor.
You will need to open the case than set the jumper setting for RS-422 mode or RS-485 mode as per the requirements of your application.
Settings are listed as follows:
Jumper | Function |
1-2 enable 2-3 disable |
Tx Termination of 120 Ohm. This jumper should always be populated for RS-485 mode. |
4-5 enable 5-6 disable |
Pull-up Tx+ to VCC by 750 Ohm Bias resistor. This jumper should be populated for pull-up Tx+. |
7-8 enable 8-9 disable |
Pull-down Tx- to GND by 750 Ohm Bias resistor. This jumper should be populated for pull-down Tx- . |
10-11 enable 11-12 disable |
Rx Termination of 120 Ohm. This jumper should always be populated for RS-422 mode. |
13-14 enable 14-15 disable |
Pull-up Rx+ to VCC by 750 Ohm Bias resistor. This jumper should be populated for pull-up Rx+. |
16-17 enable 17-18 disable |
Pull-down Rx- to GND by 750 Ohm Bias resistor. This jumper should be populated for pull-down Rx-. |
19-20 enable 20-21 disable |
CTS Termination of 120 Ohm. This jumper should always be populated for RS-422 mode. |
Note : all other positions = no jumper populated.
Sometimes, when operating in RS-422 or RS-485, it is necessary to configure 120 Ohm termination of the data transmission lines. Generally this must be done in the cabling, since this depends on the installation of connections. Before applying the option, check your cable specification for proper impedance matching.
Pin 1 | TxD- (A) |
Pin 2 | TxD+(B) |
Pin 3 | RxD+(B) |
Pin 4 | RxD-(A) |
Pin 5 | GND |
Pin 6 | RTS- (A) |
Pin 7 | RTS+(B) |
Pin 8 | CTS+(B) |
Pin 9 | CTS- (A) |
USB-COMi RS-422 Device |
USB-COMi RS-422 Device |
Pin 1 | Data- (A) |
Pin 2 | Data+(B) |
Pin 5 | GND |
USB-COMi RS-485 Device![]() |