8
Technical Support: [email protected] US: +1 866 677 0053 EU: +44 (0) 1793 230 343
INITIAL CONNECTION, IR/RS232 CONTROL CONNECTIONAND UNDERST
ANDING RS232
DB-9 DB-25
Function
1
8
DCD Data Carrier Detect
2
3
RxD Receive Data
3
2
TxD Transmit Data
4
20
DTR Data Terminal Ready
5
7
GND Ground (Signal)
6
6
DSR Data Set Ready
7
4
RTS Request to Send
8
5
CTS Clear to Send
9
22
RI
Ring Indicator
DB-9 to DB-25 Conversion
RS232 Connections
A straight-through cable should be used to connect a DTE (e.g. computer) to a DCE (e.g. Amp, Matrix or Modem), with
all signals from one side connected to the corresponding signals on the other side in a one-to-one basis.
A crossover (null-modem) cable can be used to connect two DTE directly, without a modem in between to cross
transmit and receive data signals between the two sides. There are numerous variations on how control signals are
wired:
Straight-through (DB-9
(DTE)
(DCE)
1
DCD ------- DCD 1
2
RxD ------- TxD 2
3
TxD ------- RxD 3
4
DTR ------- DSR 4
5
GND ------- GND 5
6
DSR ------- DTR 6
7
RTS ------- CTS 7
8
CTS ------- RTS 8
9
RI
------- RI
9
Crossover (Null-Modern) (DB-9
(DTE)
(DCE)
1
DCD ------- DCD 1
2
RxD ------- TxD 3
3
TxD ------- RxD 2
4
DTR ------- DSR 6
5
GND ------- GND 5
6
DSR ------- DTR 4
7
RTS ------- CTS 8
8
CTS ------- RTS 7
9
RI
RI
9
0
3
6
1
4
7
2
5
stop
start
LSB
MSB
Mark (1)
-12v
space (0)
+12v
DTE Pin Assignment (DB-9)
DCE Pin Assignment (DB-9)
1
DCD Data Carrier Detect
1
DCD Data Carrier Detect
2
RxD
Receive Data
2
TxD
Transmit Data
3
TxD
Transmit Data
3
RxD
Receive Data
4
DTR Data Terminal Ready
4
DSR Data Set Ready
5
GND Ground (Signal)
5
GND Ground (Signal)
6
DSR Data Set Ready
6
DTR Data Terminal Ready
7
RTS
Request to Send
7
CTS
Clear to Send
8
CTS
Clear to Send
8
RTS
Request to Send
9
RI
Ring Indicator
9
RI
Ring Indicator
