u-blox LEXI-R422, System Integration Manual

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LEXI-R422 - System integration manual
UBX-23007449 - R02 System description Page 23 of 108
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1.6.2 Module power-off
The graceful power-off procedure, with storage of current parameter settings in module’s non -volatile
memory and performing a clean network detach, can be triggered by:
• AT+CPWROFF command (see AT commands manual [2] )
• Low pulse on the PWR_CTRL pin for a valid time period (for detailed characteristics, see LEXI-R422
data sheet [1] )
☞
The graceful shutdown must be started as indicated above, and then a proper VCC supply must
be held at least until the end of the modules’ internal switch -off sequence, which occurs when the
generic digital interfaces supply output ( V_INT ) is switched off by the module.
A faster emergency power-off procedure of LEXI-R422, with storage of current parameter settings in
the non-volatile memory of the module, but without proper network detach, can be triggered by:
• AT+CFUN=10 command (see AT commands manual [2] )
• Forcing a rising edge at the GPIO input pin configured with the faster power-off function (see
section
1.10 , faster power-off)
The fastest memory-safe emergency power-off procedure of LEXI-R422, inhibiting further operations
in the
module’s non-volatile flash memory, without executing the storage of the current parameter
settings, and without executing a clean network detach, can be triggered by:
• AT+CFUN=11 command (see AT commands manual [2] )
•
Forcing a rising edge at the GPIO input pin configured with the memory-safe power-off function
(see section
1.10 , memory-safe power-off)
☞
The graceful shutdown procedure must be preferred to any emergency power-off procedures,
which shall be used for emergency only.
An abrupt under-voltage shutdown occurs on LEXI-R422 when the VCC voltage supply is removed,
dropping below the under-voltage shutdown threshold. 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 clean
network detach.
☞
It is highly recommended to avoid an abrupt removal of the VCC supply during LEXI-R422 modules
normal operations.
☞
If an abrupt power removal is unavoidable, it is recommended to apply a rising edge to the GPIO pin
configured with the memory-safe power-off function as soon as the power failure in the supply
source is detected, placing a low-ESR 470 mF capacitor at the
VCC supply input to let the module
complete the memory-safe emergency power-off.
⚠
An abrupt removal of the VCC supply during LEXI-R422 modules normal operations may lead to
an unrecoverable faulty state!
LEXI-R422 modules automatically switch off, with storage of the current parameter settings in the
module’s internal non -volatile memory and a clean network detach, after having sent the last gasp,
once the feature is enabled and triggered (see the AT commands manual [2] , +ULGASP AT command).