CEP AG
Revision 1.2
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5
GND
-
0 V
Ground connection
6
DSR
Output
> + 4V
< - 4 V
Data set ready
7
RTS
Input
> + 2,4V
< 0.8 V
Request to send
8
CTS
Output
> + 4V
< - 4 V
Clear to send
9
RI
Output
> + 4V
< - 4 V
Ring indicator
2.5.1 Serial Data
The modem supports the standard data character format of
Programmable baud rate
Auto-configuration mode with auto-baud.
2.5.2 Serial Data Signals
Serial Data From Modem (RD)
RD is an output signal that the modem uses to send data to the application.
Serial Data To Modem (TD)
TD is an input signal, used by the application to send data to the modem.
2.5.3 Control Signals – RTS, CTS, DTR, DSR, DCD, RI
Request to Send (RTS)
RTS is used to condition the DCE for data transmission. The default level is high by
internal pull up. The exact behaviour of RTS is defined by an AT command. Software
or Hardware control can be selected. Hardware flow is the default control. The
application must pull RTS low to communicate with the modem. The modem will
respond by asserting CTS low, indicating it is ready for communication.
Clear To Send (CTS)
CTS indicate that the DCE is ready to transmit data. The default level is high. You
can define the exact behaviour of CTS through an AT command, and can select
software or hardware flow control.
Data Terminal Ready (DTR)
DTR indicates that the DTE is ready to transmit and receive data. It also acts as
hardware ‘hang-up’, terminating calls when switched high. The signal is active low.
You can define the exact behaviour of DTR with an AT command. The DTR line can
also be used to switch on the modem when activated for 0.2 seconds. The DTR line
must be deactivated prior to switching off the modem to ensure it switches off
(powers down) correctly.
