28 -
DeviceMaster UP User Guide
: 2000451 Rev. C
Connecting Serial Devices
DB9 Null-Modem Cables (RS-232)
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.
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.
DB9 Null-Modem
Cables (RS-422)
Use the following figure if you need to build an RS-422 null-modem cable.
Note:
RS-422 pinouts are not standardized. Each peripheral manufacturer uses
different pinouts. Please refer to the documentation for the peripheral to
determine the pinouts for the signals above.
DB9 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.
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
20
5
Fe
m
a
le
DB9
3
2
7
8
6
5
1
4
Pins
RJ45
5
4
1
3
6
7
Pins
2
8
De
vic
eMa
s
te
r
TxD+
TxD-
RxD+
Signal
Fe
m
a
le
DB9
7
3
8
Pins
RxD+
RxD-
Signal
TxD+
TxD-
RxD- 2
De
vic
eMaster
DB9
1
2
3
4
5
8
6
7
Pins
DCD
RxD
TxD or TRx-
DTR
GND
CTS
DSR
RTS or TRx+
Signal
DB9
1
2
3
4
5
8
6
7
Pins
DCD
RxD
TxD or TRx-
DTR
GND
CTS
DSR
RTS or TRx+
Signal
Fe
m
a
le
RI
9
9
RI
RJ45
6
5
4
2
3
8
7
1
Pins
N/A
DB25
8
3
2
20
7
5
6
4
Pins
22
