LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 48 of 125
DCD
line will be kept to ON till the SMS command execution is completed (even if the data call release
would request the
DCD
setting to OFF).
RI signal behavior
The
RI
module output line is set by default to the OFF state (high level) at UART initialization. Then, during an
incoming call, the
RI
line is switched from OFF state to ON state with a 4:1 duty cycle and a 5 s period (ON for
1 s, OFF for 4 s, see Figure 22), until the DTE attached to the module sends the ATA string and the module
accepts the incoming data 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 22: 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
Figure 23), if the feature is enabled by the proper AT command (please refer to
u-blox AT Commands Manual
[2], AT+CNMI command).
Figure 23: RI behavior at SMS arrival
This behavior allows the DTE to stay in power saving mode until the DCE related event requests service.
In case of SMS arrival, if several events occur coincidently or in quick succession each event triggers the
RI
line
independently, although the line will not be deactivated between each event. As a result, the
RI
line may stay to
ON for more than 1 second.
If an incoming call is answered within less than 1 second (with ATA or if autoanswering is set to ATS0=1) than
the
RI
line will be set to OFF earlier.
As a result:
RI
line monitoring can’t be used by the DTE to determine the number of received SMSes.
In case of multiple events (incoming call plus SMS received), the
RI
line can’t be used to discriminate the
two events, but the DTE must rely on the subsequent URCs and interrogate the DCE with the proper
commands.
SMS arrives
time [s]
0
RI ON
RI OFF
1s
SMS
time [s]
0
RI ON
RI OFF
1s
1s
time [s]
15
10
5
0
RI ON
RI OFF
Call incomes
1s
time [s]
15
10
5
0
RI ON
RI OFF
Call incomes