User's Manual

PCS3_HD_v01.000-03
Confidential / Preliminary
Page 27 of 101
2013-10-21
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PCS3 Hardware Interface Description
3.3 Power-Up / Power-Down Scenarios
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3.3.3 Turn off PCS3 Using AT Command
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The best and safest approach to powering down PCS3 is to issue the AT^SMSO command.
This procedure lets PCS3 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. After sending AT^SMSO do not enter any
other AT commands. To verify that the module turned off it is possible to monitor the PWR_IND
signal. A high state of the PWR_IND signal line definitely indicates that the module is switched
off.
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Be sure not to disconnect the supply voltage V
BATT+
before the module has been switched off
and the PWR_IND signal has gone high. Otherwise you run the risk of losing data.
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While PCS3 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 signal lines of the application interface, especially of the serial interfaces.
No special care is required for the USB interface which is protected from reverse current.
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Power down
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PWR_IND
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BATT+ See note 1
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VEXT
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0.5ms
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See note 2
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approx.
12ms
Digital outputs
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Reset
State
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Digital inputs driven by application
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Figure 5: Signal states during turn-off procedure
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Note 1: The power supply voltage (BATT+) may be disconnected resp. switched off only after
having reached Power Down mode as indicated by the PWR_IND signal going high.
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Note 2: Depending on capacitance load from host application.
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Note 3: After module shutdown by means of AT command, please allow for a time period of at
least 1s before restarting the module.