Figure 8: Timing Of Turn Off Gsm Part - SimCom SIM548C HD V1.01 Hardware Design

SIM548C Hardware Design
3.4.2.2 Turn off the GSM part using AT command
You can use an AT command "AT+CPOWD=1" to turn off the module. This command lets the
module to log off from the network and allows the GSM part 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 commands can't be executed. The GSM part 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 ≤ 3.5V, the
following URC will be presented:
UNDER-VOLTAGE WARNNING
If the voltage ≥ 4.5V, the following URC will be presented:
OVER-VOLTAGE WARNNING
The uncritical voltage range is 3.4V to 4.6V. If the voltage ≥ 4.6V or ≤ 3.4V, the module will
SIM548C_HD_V1.01
Figure 8: Timing of turn off GSM part
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09.05.2008