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CL4490 User’s Manual
1.4 RS-232
RS-232 is a single ended data transmission protocol. The RS-232 signals are represented by
voltage levels with respect to a system common (power / logic ground). The "idle" state (MARK)
has the signal level negative with respect to common, and the "active" state (SPACE) has the
signal level positive with respect to common. RS-232 has numerous handshaking lines (primarily
used with modems), and also specifies a communications protocol.
Figure 5- RS-232 Male/Female Connector Pin out
RS-232 DB9
Female Connector RS-232 DB9 Male Connector
Pin Description
1
DCD
2 RxD
3 TxD
4 DTR
5 GND
6 DSR
7 RTS
8 CTS
9
RI
Pin Description
NC
DCD
2TxD
3RxD
4DSR
5GND
6DTR
7CTS
8RTS
NC
RI
Figure 6- DCE to DTE Interface
CL4490 Modem
OEM Host/PC
DTR
DSR
D
C
D
DTR
D
S
R
D
C
D
GN
D
GND
RXD
TXD
TXD
RXD
C
T
S
CTS
RT
S
RT
S
DCE
DTE
Straight Through Cable
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