Installation

44 - Connecting Serial Devices Hardware Installation and Configuration Guide: 2000451 Rev. J
Connecting Serial Devices
RJ45 Connectors
This subsection provides the following information:
• Connector pin assignments (below)
• RJ45 Null-Modem Cables (RS-232)
• RJ45 Null-Modem Cables (RS-422) on Page 45
• RJ45 Straight-Through Cables (RS-232/485) on Page 45
• RJ45 Loopback Plugs on Page 45
• RJ45 RS-485 Test Cable on Page 46
• Connecting RJ45 Devices on Page 46
You can build your own null-modem or straight-through RJ45 serial cables if you
are using the DB9 to RJ45 adapters using the following subsections.
RJ45 Null-Modem
Cables (RS-232)
Use the following figure if you need to build an RS-232 null-modem cable. A null-
modem cable is required for connecting DTE devices.
Note: You may want to purchase or build a straight-through cable and purchase a
null-modem adapter. For example, a null-modem cable can be used to
connect COM2 of one PC to COM2 of another PC.
Pin RS-232 RS-422 RS-485
1 RTS TxD+ TRxD+
2 DTR Not used Not used
3 Signal GND Signal GND Signal GND
4 TxD TxD- TRxD-
5RxD RxD- Not used
6 DCD Not used Not used
7 DSR Not used Not used
8CTS RxD+ Not used
DeviceMaster
TxD
RxD
RTS
CTS
DSR
GND
DCD
DTR
Signal
RxD
TxD
CTS
RTS
DTR
GND
DCD
DSR
Signal
DB9
2
3
8
7
4
5
1
6
Pins
DB25
3
2
4
7
8
6
Pins
RJ45
4
5
1
8
7
3
6
2
Pins
20
5
Female

RJ45
5
4
1
3
6
7
Pins
2
8