5 rs232 serial port – Sony Ericsson TT4031 (SE-GM29) User Manual
Page 34
Owner’s Manual
Rev 1.0
Page 34 of 34
2.5 RS232 Serial Port
The modem supports a standard RS232 serial interface (EIA/TIA 574) via
its 9 pin Sub-D connector, shown below. In line with serial communication
terminology the TT4031 (SE-GM29) serial modem should be considered as
the data circuit-terminating equipment (DCE) and the external application
or computer as the data terminating equipment (DTE).
The electrical characteristics of the serial port signals are shown below:
Pin Signal Dir Voltage
levels
Description
1
DCD
O
> +4 V
< –4 V
Data carrier detect
2
RD
O
> +4 V
< –4 V
Received data
3
TD
I
> 2 V
< 0.8 V
Transmitted data
4
DTR
I
> 2 V
< 0.8 V
Data terminal ready
5
GND
-
0 V
Ground connection
6
DSR
O
> +4 V
< –4 V
Data set ready
7
RTS
I
> 2 V
< 0.8 V
Request to send
8
CTS
O
> +4 V
< –4 V
Clear to send
9
RI
O
> +4 V
< –4 V
Ring indicator