SARA-G450 - System integration manual
UBX-18046432 - R08
System description
Page 34 of 143
C1-Public
☞
For scenarios when the DCD line setting is requested for different reasons (e.g. SMS texting
during online command mode), the DCD line changes to guarantee the correct behavior for all the
scenarios. For instance, for SMS texting in online command mode, if the call is released, the DCD
line is kept to ON till the SMS command execution is completed (even if the call release would
request the DCD setting to OFF).
If AT&C0 is set, the DCD module output line is set by default to the ON state (low level) at UART
initialization and is then always held in the ON state.
RI signal behavior
The RI module output line is set by default to the OFF state (high level) at UART initialization.
During an incoming call, the RI line is switched from the OFF state to the ON state with a 4:1 duty cycle
and a 5 s period (ON for 1 s, OFF for 4 s, see
), until the DTE attached to the module sends the
ATA string and the module accepts the incoming call. The RING string sent by the module (DCE) to
the serial port at constant time intervals is not correlated with the switch of the RI line to the ON state.
Figure 15: RI behavior during an incoming call
The RI line can notify an SMS arrival. When the SMS arrives, the RI line switches from OFF to ON for
1 s (see
), if the feature is enabled by the AT+CNMI command (see the u-blox AT commands
Figure 16: RI behavior at SMS arrival
This behavior allows the DTE to stay in power saving mode until the DCE related event requests
service.
1s
time [s]
15
10
5
0
RI ON
RI OFF
Call incomes
1s
time [s]
15
10
RI ON
RI OFF
Call incomes
SMS arrives
time [s]
0
RI ON
RI OFF
1s
SMS
time [s]
RI ON
RI OFF
1s