Comtrol DM AIR - Manual (Page 33)

Connecting Serial Devices DeviceMaster AIR User Guide: 2000365 Rev. C - 33
DB9 Serial Cables and Loopback Plugs
DB9 Serial Cables and Loopback Plugs
You can build your own null-modem or straight-through DB9 serial cables using
the following subsections.
This illustrates the DB9 connector signals.
DB9 Loopback Plugs Loopback connectors are DB9 female serial port plugs, with pins wired together as
shown, that are used in conjunction with application software (Test Terminal or
Minicom) to test serial ports. The DeviceMaster AIR is shipped with a a single
loopback plug (RS-232/422).
Note: See the appropriate NS-Link guide for information about using Test
Terminal or Minicom to test the serial ports (see Locating Software and
Documentation on Page 8).
Wire the following pins together to build additional plugs or replace a missing RS-
232 loopback plug:
• Pins 1 to 4 to 6
• Pins 2 to 3
• Pins 7 to 8 to 9
Wire the following pins together for an RS-422 loopback plug:
• Pins 2 to 3
• Pins 7 to 8
DB9 Connector Pinouts
Pin RS-232 RS-422 RS-485
1 DCD Not used Not used
2 RxD RxD- Not used
3 TxD TxD- TxD/RxD-
4 DTR Not used Not used
5 GND Not used† Not used†
6 DSR Not used Not used
7 RTS TxD+ TxD/RxD+
8 CTS RxD+ Not used
9 RI Not used Not Used
† Pin 5 is tied to ground on the board, but is
not used in the cable.
Pin 1
Pin 6
DB9 Male
RS-232
RI
CTS
RTS
DSR
GND
DTR
TxD
RxD
CD
Pin 1
Pin 6
DB9 Male
RS-422
Not used
RxD+
TxD+
Not used
Not used*
Not used
TxD-
RxD-
Not used
Pin 1 Pin 6
DB9 Male
RS-485
Not used
Not used
TxD/RxD+
Not used
Not used*
Not used
TxD/RxD-
Not used
Not used
* Pin 5 is tied to ground on the board,
but is not used in the cable.
Pin 1 Pin 5
Pin 6 Pin 9
RS-232 Only
(Back View) The RS-232 loopback plug
also works for RS-422.
Pin 1 Pin 5
Pin 6 Pin 9
RS-422 Only
(Back View)