Electrical Description
INSYS GPRS mini
4.6
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.
4.7
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.
Data Set Ready (DSR)
An active DSR signal is sent from the modem to the application (DTE) to con-
firm that a communications path has been established. DSR has two modes
of operation, settable using the AT command AT&S.
Data Carrier Detect (DCD)
DCD indicates that the DCE is receiving a valid carrier (data signal) when
low. You can define the exact behaviour of DCD with an AT command.
Ring Indicator (RI)
RI indicates that a ringing signal is being received by the DCE when low. You
can define the exact behaviour for RI with an AT command.
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