Rj45 Null-Modem Cables (Rs-422); Rj45 Straight-Through Cables (Rs-232/485); Rj45 Loopback Plugs; Rj45 Rs-485 Test Cable - Comtrol DeviceMaster DM-2000 Series Installation And Configuration Manual

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
Ports Using Test Terminal
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.
92 - Connecting Serial Devices
RJ45
Signal
Pins
TxD+
1
TxD- 4
RxD+ 8
RxD- 5
GND 3
RJ45
Signal Pins
6
DCD
5
RxD
4
TxD or TRxD-
2
DTR
3
GND
DSR 7
1
RTS or TRxD+
8
CTS
on Page 154 for Windows
RJ45
Signal Pins
4
TRxD-
1
TRxD+
Signal
RxD+
RxD-
TxD+
TxD-
GND
DB9 RJ45 DB25
Pins
Pins Pins Signal
6
1 8
DCD
2 5
3
RxD
3 4
2
TxD or TRxD-
4 2 20
DTR
3
5 7
GND
6 7
6 DSR
7 1
4
RTS or TRxD+
8 8
5
CTS
1 8
Plug
Top View
Cable
Testing
Signal
TRxD-
TRxD+
DeviceMaster Installation and Configuration Guide: 2000594 Rev. F
The RS-232 loopback plug also
works for RS-422.