Serial terminal (8) null-modem cables (rs-422), Serial terminal (8) loopback signals – Comtrol UP DeviceMaster Installation User Manual
Page 51
Hardware Installation and Configuration Guide: 2000451 Rev. J
Connecting Serial Devices - 51
Connecting Serial Devices
Serial Terminal (8)
Null-Modem Cables
(RS-422)
An RS-422 null-modem cable is
required for connecting DTE
devices.
Serial Terminal (8)
Straight-Through
Cables (RS-232/485)
RS-232 or RS-485 straight-
through cables are used to
connect modems and other
DCE devices.
Serial Terminal (8)
Loopback Signals
Use the drawing below to wire a loopback, which is used in conjunction with
application software to test serial ports.
Wire the terminals together to
create a loopback.
•
TxD to RxD
•
RTS to CTS to RI
•
DTR to CD to DSR
CD DSR RI DTR
RTS
TxD
RxD CTS
RxD+
RxD-
TxD- TxD+
8
2
3
7
5
3
2
4
DB9
DB25
RS-422 Null-Modem Cable
RS-232/485 Straight-Through Cable
CD
DSR
RI
DTR
RTS
TxD
RxD CTS
DCD DSR
RI
DTR
RTS
TxD
RxD
CTS
1
6
9
7
2
8
6
22
20
4
2
3
5
DB9
DB25
3
4
8
or
TRxD-
or
TRxD+
TxD
RxD
RTS
CTS
CD DSR
RI
DTR