MC75i Hardware Interface Description
3.3 Power Up / Power Down Scenarios
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MC75i_HD_v01.100a
Page 34 of 122
2009-08-13
Confidential / Released
3.3.3
Turn off MC75i
MC75i 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 und-
ervoltage or overvoltage conditions occur.
3.3.3.1
Turn off MC75i Using AT Command
The best and safest approach to powering down MC75i is to issue the AT^SMSO command.
This procedure lets MC75i log off from the network and allows the software to enter into a se-
cure 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 signal. High state of PWR_IND definitely indicates that
the module is switched off.
Be sure not to disconnect the supply voltage V
BATT+
before the URC “^SHUTDOWN” has been
issued and the PWR_IND signal has gone high. Otherwise you run the risk of losing data. Sig-
nal states during turn-off are shown in
While MC75i 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 lines of the application interface, especially of the serial interfaces. No spe-
cial care is required for the USB interface which is protected from reverse current.
