Users Manual

GSM/GPRS Module Series
M66 Hardware Design
M66_Hardware_Design Confidential / Released 30 / 82
1. This unsolicited result codes do not appear when autobauding is active and DTE and DCE are not
correctly synchronized after start-up. The module is recommended to set to a fixed baud rate.
2. As logout network time is related to the local mobile network, it is recommended to delay about 12
seconds before disconnecting the power supply or restarting the module.
3.4.2.2. Power Down Module Using AT Command
It is also a safe way to turn off the module via AT command AT+QPOWD=1. This command will let the
module log off from the network and allow the firmware to save important data before completely
disconnecting the power supply.
Before the completion of the power down procedure the module sends out the result code shown below:
NORMAL POWER DOWN
After that moment, no further AT commands can be executed. And then the module enters the power
down mode, only the RTC is still active.
Please refer to the document [1] for details about the AT command AT+QPOWD.
3.4.2.3. Under-voltage Automatic Shutdown
The module will constantly monitor the voltage applied on the VBAT, if the
voltage is ≤3.5V, the following URC will be presented:
UNDER_VOLTAGE WARNING
The normal input voltage range is from 3.3V to 4.6V. If the voltage is <3.3V, the module would
automatically shut down itself.
If the voltage is <3.3V, the following URC will be presented:
UNDER_VOLTAGE POWER DOWN
After that moment, no further AT commands can be executed. The module logs off from network and
enters power down mode, and only RTC is still active.