CHAPTER 6
RS422/RS485 CABLING INFORMATION

6.1  RS422 Cabling Information for DB9
The communication interface follows the EIA RS422 standard. The signal assignments for a standard DB9 connector are shown below :

Pin

Description

1

Chassis Ground (GND)

4

Transmit Data+(TxD+)

5

Transmit Data-(TxD-)

8

Receive Data+(RxD+)

9

Receive Data-(RxD-)

To connect the RS422 to other DATA TERMINAL EQUIPMENT (DTE) devices, the developers recommend using a DTE to DTE connection as shown below.

HOST

REMOTE

    Chassis Ground

    Chassis Ground

    Transmit Data(+)

    Receive Data(+)

    Receive Data(+)

    Transmit Data(+)

    Transmit Data(-)

    Receive Data(-)

    Receive Data(-)

    Transmit Data(-)

6.2  RS485 Cabling Information for DB25

The RS485 signal assignment is shown as follows.

Pin

Description

1

  Signal Ground

4

  Transmit Data+(TxD+)

5

  Transmit Data-(TxD-)

8

  Receive Data+(RxD+)

9

  Receive Data-(RxD-)

The RS485 communication is based on cable sharing method, which is connected as following:

Computer at site 1

Computer at site 2

TRD+

TRD+

TRD–

TRD–

Ground

Ground

Where TRD+ means short pin 4 and pin 8 at connector side, and TRD- means short pin 5 and pin 9 at connector side. You must short both pins by yourself.

6.3 RS422 Cabling Information for DB25

The communication interface follows the EIA RS422 standard. The signal assignments for a standard DB25 connector are shown below:

Pin

Description

1

Transmit Data-(TxD-)

5

Receive Data+(RxD+)

     7

Chassis Ground (GND)

20

Transmit Data+(TxD+)

22

Receive Data-(RxD-)