12 - Connecting Serial Devices
RocketPort EXPRESS User Guide
: 2000481 Rev. G
DB9 Signals
DB9 Signals
Refer to the manufacturer’s installation documentation if you need help with the
connector pinouts or cabling for the serial device.
DB9 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.
If you need RTS-CTS/DTR-DSR
hardware flow control, you can use
the pinouts provided in the
following example.
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.
Note:
RJ45 connectors are not
standardized. Refer to your
serial device documentation
for signal information.
DB9 Null-Modem
Cables (RS-422 or
RS-485 Full-Duplex)
Use the following figure if you need to build
an RS-422 or RS-485 full-duplex null-modem
cable. A null-modem cable is required for
connecting DTE devices.
Note:
RS-422 and RS-45 signals are not
standardized and each serial
manufacturer uses different pinouts.
Refer to the serial device
documentation to determine the
pinouts for the signals above.
DB9 Male Connector Signals
Pin
RS-232
RS-422
RS-485
(Full-Duplex)
RS-485
(Half-Duplex)
1
DCD
Not used
Not used
Not used
2
RxD
RxD-
RxD-
Not used
3
TxD
TxD-
TxD-
TRxD-
4
DTR
Not used
Not used
Not used
5
SIG GND
SIG GND
SIG GND
SIG GND
6
DSR
Not used
Not used
Not used
7
RTS
TxD+
TxD+
TRxD+
8
CTS
RxD+
RxD+
Not used
9
RI
Not used
Not Used
Not Used
Ground must be tied to signal ground.
Pin 1
Pin 5
Pin 6
Pin 9
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
20
5
DB9
3
2
7
8
6
5
1
4
Pins
RI
RI
9
22
9
RocketPort DTE
Serial
Device
TxD+
TxD-
RxD+
Signal
DB9
7
3
8
Pins
RxD+
RxD-
Signal
TxD+
TxD-
RxD- 2
RocketPort
DTE Serial
Device
