B&B Electronics ESP901 - RS-232 Straight-Through Cable Connections; RS-232 Crossover (Null Modem) Cable Connections

RS-232 Connections
72 Appendix A Manual Documentation Number: ESP901-902_5012m
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104 – www.bb-elec.com
B&B Electronics Ltd – Westlink Commercial Pk – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445 – www.bb-europe.com
RS-232 Straight-through Cable Connections
In the RS-232 mode, the Serial Server’s ports are configured as DTEs
like a computer. If the device connected to the Serial Server is
configured as a DCE use a straight through cable wired as shown
below:
Figure 61. Straight-through DB-9 to DB-9 RS-232 Serial Cable
RS-232 Crossover (null modem) Cable Connections
When connecting to a PC or another DTE device, use a crossover cable
(also called a null modem cable).
Figure 62. Crossover DB-9 to DB-9 RS-232 Serial Cable
RS-232 Signal Names
DB-9
Pin#
Connections
DB-9
Pin#
Signal
Carrier Detect
CD
1
1
CD
Receive Data
RD
2
2
RD
Transmit Data
TD
3
3
TD
Data Terminal Ready
DTR
4
4
DTR
Signal Ground/Common
GND
5
5
GND
Data Set Ready
DSR
6
6
DSR
Request to Send
RTS
7
7
RTS
Clear to Send
CTS
8
8
CTS
Ring Indicator
RI
9
9
RI
RS-232 Signal Names
DB-9
Pin#
Connections
DB-9
Pin#
Signal
Carrier Detect
CD
1
1
CD
Receive Data
RD
2
2
RD
Transmit Data
TD
3
3
TD
Data Terminal Ready
DTR
4
4
DTR
Signal Ground/Common
GND
5
5
GND
Data Set Ready
DSR
6
6
DSR
Request to Send
RTS
7
7
RTS
Clear to Send
CTS
8
8
CTS
Ring Indicator
RI
9
9
RI