SIM900 Hardware Design
3.4.2.2 Turn Off SIM900 Using AT Command
You can use the AT command “AT+CPOWD=1” to turn off the module. This command lets the module log off
from the network and allows the module to enter into a secure state and save data before completely disconnecting
the power supply.
Before the completion of the switching off procedure the module will send out result code:
NORMAL POWER DOWN
After this moment, the AT commands can’t be executed. The module enters the POWER DOWN mode, only the
RTC is still active. POWER DOWN can also be indicated by STATUS pin, which is a low level voltage in this
mode.
Please refer to document [1] for detail about the AT command of “AT+CPOWD”.
3.4.2.3 Over-voltage or Under-voltage Automatic Shutdown
The module will constantly monitor the voltage applied on the VBAT. If the voltage ≤ 3.15V, the following URC
will be presented:
UNDER-VOLTAGE WARNNING
If the voltage ≥ 4.7V, the following URC will be presented:
OVER-VOLTAGE WARNNING
The uncritical voltage range is 3.1V to 4.8V. If the voltage > 4.8V or < 3.1V, the module will be automatic
shutdown soon.
If the voltage < 3.1V, the following URC will be presented:
UNDER-VOLTAGE POWER DOWN
If the voltage > 4.8V, the following URC will be presented:
OVER-VOLTAGE POWER DOWN
After this moment, no further more AT commands can be executed. The module logs off from network and enters
POWER DOWN mode, and only the RTC is still active. POWER DOWN can also be indicated by STATUS pin,
which is a low level voltage in this mode.
3.4.2.4 Over-temperature or Under-temperature Automatic Shutdown
The module will constantly monitor the temperature of the module, if the temperature > 80 , the following ℃
URC will be presented:
+CMTE:1
If the temperature < -30 , the following URC will be presented:℃
+CMTE:-1
The uncritical temperature range is -40 to ℃ +85 . If the temperature ℃ > +85 or ℃ < -40 , the module will be ℃
automatic shutdown soon.
If the temperature > +85 , the following URC will be presented:℃
+CMTE:2
If the temperature < -40℃, the following URC will be presented:
+CMTE:-2
SIM900_HD_V1.05 06.23.2010
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