User's Manual

SARA-R4 series - System Integration Manual
UBX-16029218 - R03 System description
Page 18 of 94
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 [2].
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 the application can monitor the V_INT pin
to sense the end of the switch-off sequence.
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.