International Network Router User Manual

Digi TransPort
®
WR21 Installation Guide
Page 19
Appendix A: SERIAL 0 Port Pin-out Diagram
WWAN
SECONDARY
SERIAL 0
9-30VDC
2A MAX
WWAN
PRIMARY
LAN 1LAN 0
SERIAL 0
Pin 1
Pin 9
RS232
Pin # Direction RS232 DCE Description
1 Out DCD Data Carrier Detect
2 Out RXD Receive Data
3 In TXD Transmit Data
4 In DTR Data Terminal Ready
5 N/A GND Ground
6 Out DSR Data Set Ready
7 In RTS Ready To Send
8 Out CTS Clear To Send
9 Out RI Ring Indicate
RS422/ RS485
Pin # Direction RS422/
RS485
Description
1 Out CTS_B Clear To Send B
2 Out RD_A Receive Data A
3 In TD_A Transmit Data A
4 In RTS_B Ready To Send B
5 N/A GND Ground
6 Out RD_B Receive Data B
7 In RTS_A Ready To Send A
8 Out CTS_A Clear To Send A
9 In TD_B Transmit B
Notes:
For true RS485 mode (2-wire half-duplex mode), the TD_A and RD_A pair and TD_B and RD_B pair should
be connected together.
The CTS and RTS signals for optional and not normally needed for RS485.