USB-2COMi-M/USB-2COMi-SI-M Hardware Settings and Pinouts

Outside the unit, there are two 3-pin DIP switches used to select the mode of operation. You can switch to RS-422 mode or RS-485 mode as per the requirements of your application.

 

RS-422 & RS-485 Mode Configuration

 

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

 

Termination & Bias Resistor Configuration

Inside the unit, there are two 7 × 2 (14 pin) header blocks which are jumpered to enable Tx, Rx, CTS 120Ω termination resistors and Rx, Tx 750Ω biasing resistors.

You will need to open up the case to set the jumper settings as per the requirements of your application.

 

Jumper Function
1-2 Tx+/- termination of 120Ω.This jumper should always be populated for RS-485 half-duplex mode.
3-4 Pull-up Tx+ to VCC by 750Ω bias resistor. This jumper should be populated for pull-up Tx+.
5-6 Pull-down Tx- to GND by 750Ω bias resistor. This jumper should be populated for pull-down Tx-.
7-8 Rx+/- termination of 120Ω. This jumper should always be populated for RS-422 and RS-485 full-duplex mode.
9-10 Pull-up Rx+ to VCC by 750Ω bias resistor. This jumper should be populated for pull-up Rx+.
11-12 Pull-down Rx- to GND by 750Ω bias resistor. This jumper should be populated for pull-down Rx-.
13-14 CTS termination of 120Ω. 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, termination is disabled by default.

 

RS-422/485 Pinouts

 

 

RS-422 DB9 Male Connector Pinouts

 

PIN SIGNAL
1 TxD- (A)
2 TxD+ (B)
3 RxD+ (B)
4 RxD- (A)
5 GND
6 RTS- (A)
7 RTS+ (B)
8 CTS+ (B)
9 CTS- (A)

 

RS-422 Terminal Block Pinouts

 

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

 

RS-485 4-Wire (Full duplex) DB9 Male Connector Pinouts

 

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

 

RS-485 4-Wire (Full duplex) Terminal Block Pinouts

 

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

 

RS-485 2-Wire (Half duplex) DB9 Male Connector Pinouts

 

PIN SIGNAL
1 Data- (A)
2 Data+ (B)
5 GND

 

RS-485 2-Wire (Half duplex) Terminal Block Pinouts

 

PIN SIGNAL
1 Data- (A)
2 Data+ (B)
5 GND

 

RS-422/485 Signal Wiring

RS-422

Point-to-Point 4 Wire Full Duplex

 

 

RS-422 with Handshaking

 

 

RS-485

Point-to-Point 4 Wire Full Duplex

 

 

Multidrop RS-485 2-Wire Half-duplex