18 - Connecting Serial Devices
RocketPort EXPRESS User Guide
: 2000481 Rev. G
RJ45 Null-Modem Cable (RS-232)
RJ45 Null-Modem
Cable (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.
RJ45 Null-Modem
Cable (RS-422 or RS-
485 Full-Duplex)
Use the following figure if you need to build
an RS-422 null-modem cable. A null-modem
cable is required for connecting DTE
devices.
Note:
RS-422 pinouts are not standardized.
Each serial manufacturer uses
various pinouts. Please refer to the
documentation for the serial to
determine the pinouts for the signals in the previous picture.
RJ45 Straight-
Through Cable (RS-
232 or RS-485 Half-
Duplex)
Use straight-through cables to connect modems and other DTE devices. For
example, you can connect one end of a straight-through cable to COM2 on one
computer and the other end of the straight-through cable to a modem.
RJ45 Loopback
Plugs
RocketPort EXPRESS models with RJ45 connectors are shipped with
a a single loopback plug (RS-232/422).
Wire the following pins together to build additional loopback plugs or
replace a missing RS-232/422 loopback plug:
•
Pins 4 to 5
•
Pins 1 to 8
•
Pins 2 to 6 to 7
Wire the following pins together for an RS-422 loopback plug:
•
Pins 4 to 5
•
Pins 1 to 8
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
RocketPort
DTE Serial Device
TxD+
TxD-
RxD+
Signal
RJ45
1
4
8
Pins
RxD+
RxD-
Signal
RxD- 5
TxD+
TxD-
DTE Serial
Device
RocketPort
DB9
1
2
3
4
5
8
6
7
Pins
DCD
RxD
TxD TRxD-
DTR
GND
CTS
DSR
RTS TRxD+
Signal
DCD
RxD
TxD TRxD-
DTR
GND
CTS
DSR
RTS TRxD+
Signal
RI
9
RJ45
6
5
4
2
3
8
7
1
Pins
N/A
DB25
8
3
2
20
7
5
6
4
Pins
22
RI
RocketPort
DCE Serial Device
RS-232 RS-485HD
RS-232 RS-485HD
RS-232/422
