USB-8COMi-M Hardware Settings and Pinouts

Outside the unit, there are eight 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. You need to install the driver first, prior to hardware installation. After setting the operation mode and connecting power supply to the adapter, you can then plug the adapter to a USB port to start driver installation.

 

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

You will need to open up the metal 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 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 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.

 

RS-422/485 DB9 Male Connector 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-485 4-Wire (Full duplex) DB9 Male Connector Pinouts

 

PIN SIGNAL
1 Tx- (A)
2 Tx+ (B)
3 Rx+ (B)
4 Rx- (A)
5 GND

 

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