SARA-R4 series - System Integration Manual
UBX-16029218 - R06
System description
Page 20 of 102
1.6.2
Module power-off
SARA-R4 series can be properly switched off by:
AT+CPWROFF command (see
SARA-R4 series
AT Commands Manual
[2]). The current parameter settings are
saved in the module’s non-volatile memory and a proper network detach is performed.
Low pulse on the
PWR_ON
pin for a valid time period (see
SARA-R4 series
Data Sheet
[1]).
An abrupt under-voltage shutdown occurs on SARA-R4 series modules when the
VCC
module supply is
removed. If this occurs, it is not possible to perform the storing of the current parameter settings in the module’s
non-volatile memory or to perform the proper network detach.
It is highly recommended to avoid an abrupt removal of the
VCC
supply during SARA-R4 series modules
normal operations.
An abrupt hardware shutdown occurs on SARA-R4 series modules when a low level is applied on
RESET_N
pin.
In this case, the current parameter settings are not saved in the module’s non-volatile memory and a proper
network detach is not performed.
It is highly recommended to avoid an abrupt hardware shutdown of the module by forcing a low level on
the
RESET_N
input pin during module normal operation: the
RESET_N
line should be set low only if reset
or shutdown via AT commands fails or if the module does not reply to a specific AT command after a time
period longer than the one defined in the
SARA-R4 series
AT Commands Manual
Figure 6 describes the SARA-R4 series modules switch-off sequence started by means of the AT+CPWROFF
command, allowing storage of current parameter settings in the module’s non-volatile memory and a proper
network detach, with the following phases:
When the +CPWROFF AT command is sent, the module starts the switch-off routine.
The module replies OK on the AT interface: the switch-off routine is in progress.
At the end of the switch-off routine, all the digital pins are tri-stated and all the internal voltage regulators
are turned off, including the generic digital interfaces supply (
V_INT
).
Then, the module remains in switch-off mode as long as a switch on event does not occur (e.g. applying a
proper low level to
PWR_ON
), and enters not-powered mode if the supply is removed from the
VCC
pins.
VCC
PWR_ON
RESET_N
V_INT
Internal Reset
System State
BB Pads State
Operational
OFF
Tristate / Floating
ON
Operational
→
Tristate
AT+CPWROFF
sent to the module
OK
replied by the module
VCC can be
removed
Figure 6: SARA-R4 series switch-off sequence by means of AT+CPWROFF command
The Internal Reset signal is not available on a module pin, but it is recommended to monitor the
V_INT
pin to sense the end of the switch-off sequence:
VCC
supply can be removed only after
V_INT
goes low.
The duration of each phase in the SARA-R4 series modules’ switch-off routines can largely vary depending
on the application / network settings and the concurrent module activities.
