Comtrol DeviceMaster PRO - RJ45 Null-Modem Cables (RS-422); RJ45 Straight-Through Cables (RS-232;485); RJ45 Loopback Plugs; RJ45 RS-485 Test Cable

92 - Connecting Serial Devices DeviceMaster Installation and Configuration Guide: 2000594 Rev. F
Connecting Serial Devices
RJ45 Null-Modem Cables (RS-422)
Use the following figure if you need to build an RS-422 null-modem RJ45 cable. A null-modem cable is
required for connecting DTE devices.
Note: RS-422 pin outs are not standardized. Each peripheral manufacturer uses different pin outs. Please
refer to the documentation for the peripheral to determine the pin outs for the signals above.
RJ45 Straight-Through Cables (RS-232/485)
Use the following figure if you need to build an RS-232 or RS-485 straight-through cable. Straight-through
cables are used to connect modems and other DCE devices. For example, a straight-through cable can be used
to connect COM2 of one PC to COM2 to a modem.
RJ45 Loopback Plugs
Loopback connectors are RJ45 serial port plugs with pins wired together that are used in conjunction with
application software (Test Terminal for Windows or Minicom for Linux) to test serial ports. The DeviceMaster
is shipped with a a single loopback plug (RS-232/422).
•Pins 4 to 5
•Pins 1 to 8
•Pins 2 to 6 to 7
Note: You can use Test Terminal (Windows) or minicom
(Linux) to test the serial port. You can refer to
Testing
Ports Using Test Terminal on Page 154 for Windows
systems.
RJ45 RS-485 Test Cable
You can use a straight-through cable as illustrated previously, or build your own cable.
Note: RS-422 pin outs are not standardized. Each peripheral manufacturer uses different pin outs. Please
refer to the documentation for the peripheral to determine the pin outs for the signals above.
DeviceMaster
TxD+
TxD-
RxD+
Signal
RJ45
1
4
8
Pins
Female
RxD+
RxD-
Signal
RxD- 5
TxD+
TxD-
GND 3
GND
DeviceMaster
DB9
1
2
3
4
5
8
6
7
Pins
DCD
RxD
TxD or TRxD-
DTR
GND
CTS
DSR
RTS or TRxD+
Signal
DCD
RxD
TxD or TRxD-
DTR
GND
CTS
DSR
RTS or TRxD+
Signal
Female
RJ45
6
5
4
2
3
8
7
1
Pins
RJ45
6
5
4
2
3
8
7
1
Pins
DB25
8
3
2
20
7
5
6
4
Pins
18
Plug
Top View
Cable
The RS-232 loopback plug also
works for RS-422.
TRxD-
TRxD+
Signal
TRxD-
TRxD+
Signal
RJ45
4
1
Pins