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AC75 Hardware Interface Description
Strictly confidential / Preliminary
3.3.3 Turn off AC75
AC75 can be turned off as follows:
•
Normal shutdown: Software controlled by AT^SMSO command
•
Automatic shutdown: Takes effect if board or battery temperature is out of range or if
undervoltage or overvoltage conditions occur.
3.3.3.1
Turn off AC75 Using AT Command
The best and safest approach to powering down AC75 is to issue the AT^SMSO command.
This procedure lets AC75 log off from the network and allows the software to enter into a
secure state and safe data before disconnecting the power supply. The mode is referred to
as Power-down mode. In this mode, only the RTC stays active.
Before switching off the device sends the following response:
^SMSO: MS OFF
OK
^SHUTDOWN
After sending AT^SMSO do not enter any other AT commands. There are two ways to verify
when the module turns off:
•
Wait for the URC "^SHUTDOWN". It indicates that data have been stored non-volatile
and the module turns off in less than 1 second.
•
Also, you can monitor the PWR_IND pin. High state of PWR_IND definitely indicates that
the module is switched off.
Be sure not to disconnect the supply voltage V
been issued and the PWR_IND signal has gone high. Otherwise you run the risk of losing
data. Signal states during turn-off are shown in Figure 8.
While AC75 is in Power-down mode the application interface is switched off and must not be
fed from any other source. Therefore, your application must be designed to avoid any current
flow into any digital pins of the application interface, especially of the serial interfaces. No
special care is required for the USB interface which is protected from reverse current.
AC75_HD_V00.202
before the URC "^SHUTDOWN" has
BATT+
Page 34 of 120
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27.04.2006
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