Outside the unit, there is one 4-pin DIP switch which is set to select the mode of operation. You will need to set the switch settings to RS-422, or RS-485 mode as per the requirements of your application.
After the setting of DIP switch, you then plug the adapter to USB port to start driver installation. The Mode Block Configuration Settings are listed as follows
SW (External DIP Switch)
Operation Mode | S1 | S2 | S3 | S4 | |
RS-422 | 4 wire with Handshaking | ON | ON | OFF |
OFF |
RS-485 | Full Duplex (4 wire) | ON | OFF |
OFF |
OFF |
Half Duplex (2 wire) - with Echo | OFF |
OFF |
OFF |
ON Note |
|
Half Duplex (2 wire) - without Echo | OFF |
OFF |
ON | ON Note |
Note : In the most common situation , an 120 Ohm termination resistor of TxD (S4 is ON ) is required in RS485 Half Duplex configuration. Otherwise it is rarely used.
Inside the unit, there is one 2 x 6 (12 pin) header blocks which are jumpered to enable Rx, CTS 120 Ohm termination resistors and Tx, Rx 750 Ohm BIASing resistor. You will need to open up the metal 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:
Jumper | Function |
1-2 | Pull-up Tx+ to VCC by 750 Ohm Bias resistor. This jumper should be populated for pull-up Tx+. |
3-4 | Pull-down Tx- to GND by 750 Ohm Bias resistor. This jumper should be populated for pull-down Tx- . |
5-6 | Rx Termination of 120 Ohm. This jumper should always be populated for RS-422 mode. |
7-8 | Pull-up Rx+ to VCC by 750 Ohm Bias resistor. This jumper should be populated for pull-up Rx+ |
9-10 | Pull-down Rx- to GND by 750 Ohm Bias resistor.This jumper should be populated for pull-down Rx- . |
11-12 | CTS Termination of 120 Ohm. This jumper should 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 Pin-outs & Signal Wiring
Pin 1 | Tx- (A) |
Pin 2 | Tx+(B) |
Pin 3 | Rx+(B) |
Pin 4 | Rx- (A) |
Pin 5 | GND |
Pin 6 | RTS- (A) |
Pin 7 | RTS+(B) |
Pin 8 | CTS+(B) |
Pin 9 | CTS- (A) |
Pin 1 | Tx- (A) |
Pin 2 | Tx+(B) |
Pin 3 | Rx+(B) |
Pin 4 | Rx-(A) |
Pin 5 | GND |
Pin 6 | GND |
Point-to-Point 4-Wire Full Duplex
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RS-422 with Handshaking
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Pin 1 | Tx- (A) |
Pin 2 | Tx+(B) |
Pin 3 | Rx+(B) |
Pin 4 | Rx-(A) |
Pin 5 | GND |
Pin 1 | Tx- (A) |
Pin 2 | Tx+(B) |
Pin 3 | Rx+(B) |
Pin 4 | Rx-(A) |
Pin 5 | GND |
Pin 6 | GND |
Pin 1 | Data- (A) |
Pin 2 | Data+(B) |
Pin 5 | GND |
Pin 1 | Data- (A) |
Pin 2 | Data+(B) |
Pin 5 | GND |
Pin 6 | GND |
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