Hardware Setting & Mode Configuration

Outside the unit, there are two 3-pin DIP switches which are set to select the mode of operation. You will need to set the switch settings to RS-422 mode, or RS-485 mode, as per the requirements of your application.  The RS-422 & RS-485 Mode Block Configuration Settings are listed as follows.

 

RS-422 & RS-485 Mode Block Configuration

 

SW1 (PORT1), SW2 (PORT2)

 

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

 

Inside the unit, there are two 7x2 (14pin) header blocks which are jumpered to enable Tx,Rx, CTS 120 Ohm termination resistors and Rx, Tx 750 Ohm biasing resistor. You will need to open up the case and set the jumper setting for RS-422 mode or RS-485 mode as per the requirements of your application.

 

Settings are listed as follows:

 

JP2 (PORT1), JP3 (PORT2)

for Termination and Biasing Option Configuration

 

Jumper Function
1-2 Tx+/- Termination of 120 Ohm.This jumper should always be populated for RS485 Half-Duplex mode.
3-4 Pull-up Tx+ to VCC by 750 Ohm Bias resistor. This jumper should be populated for pull-up Tx+.
5-6 Pull-down Tx- to GND by 750 Ohm Bias resistor. This jumper should be populated for pull-down Tx-.
7-8 Rx+/- Termination of 120 Ohm. This jumper should always be populated for RS-422 and RS485 Full-Duplex mode.
9-10 Pull-up Rx+  to VCC by 750 Ohm Bias resistor. This jumper should be populated for pull-up Rx+.
11-12 Pull-down Rx- to GND by 750 Ohm Bias resistor.This jumper should be populated for pull-down Rx-.
13-14 CTS Termination of 120 Ohm. This jumper should always be populated for RS-422 mode.

 

Note : Sometimes, when operating in RS-422 or RS-485, it is necessary to configure termination and biasing 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.

 

Biasing of data lines must only occur at a single point anywhere in the cabling. USB-2COMi-M and USB-2COMi-SI-M provide biasing for ease of installation. Please be sure to disable this inside the unit, if your cabling already provides biasing.

 

Termination must not be installed in the middle of the cable. It is only permitted at both ends. Since a computer controlled serial port is almost always at one end of the cable, is enabled by default.

 

RS-422/485 Pin-outs & Signal Wiring

RS-422 Signal Pin-outs of DB-9 Male (CN2, CN3)

 

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)

 

RS-422 Signal Pin-outs of Terminal Block (TB1, TB2)

 

Pin 1 TxD- (A)
Pin 2 TxD+(B)
Pin 3 RxD+(B)
Pin 4 RxD-(A)
Pin 5 GND

 

RS-422 Signal Wiring

 

Point-to-Point 4-Wire Full Duplex

 

RS-422 with Handshakin

 

RS-485 4-Wire (Full duplex) Signal Pin-outs of DB-9 Male (CN2, CN3)

 

Pin 1 TxD- (A)
Pin 2 TxD+(B)
Pin 3 RxD+(B)
Pin 4 RxD-(A)
Pin 5 GND

 

RS-485 4-Wire (Full duplex) Signal Pin-outs of Terminal Block (TB1, TB2)

 

Pin 1 TxD- (A)
Pin 2 TxD+(B)
Pin 3 RxD+(B)
Pin 4 RxD-(A)
Pin 5 GND

 

RS-485 2-Wire (Half duplex) Signal Pin-outs of DB-9 Male (CN2, CN3)

 

Pin 1 Data- (A)
Pin 2 Data+(B)
Pin 5 GND

 

RS-485 2-Wire (Half duplex) Signal Pin-outs of Terminal Block (TB1, TB2)

 

Pin 1 Data- (A)
Pin 2 Data+(B)
Pin 5 GND  

 

RS-485 Signal Wiring

 

Point-to-Point 4-Wire Full Duplex

 

Multidrop RS-485 2-Wire Half-duplex