User Manual

XT55/56 Hardware Interface Description
Confidential / Preliminary
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XT55/56_hd_v02.96 Page 35 of 125 18.08.2005
Table 5: AT commands available in Alarm mode
AT command Function
AT+CALA Set alarm time
AT+CCLK Set date and time of RTC
AT^SBC In Alarm mode, you can only query the present current consumption and check
whether or not a charger is connected. The battery capacity is returned as 0,
regardless of the actual voltage (since the values measured directly on the cell are
not delivered to the module).
AT^SCTM Query temperature range, enable/disable URCs to report critical temperature
ranges
AT^SMSO Power down GSM engine
For the GSM engine to change from the Alarm mode to full operation (normal operating
mode) it is necessary to drive the ignition line to ground. This must be implemented in your
host application as described in Chapter 3.3.1.1.
If the charger is connected to the GSM_POWER line when GSM part of the XT55/56 is in
ALARM mode charging will start, while XT55/56 stays in ALARM mode. See also Chapter 3.7
which summarizes the various options of changing the mode of operation.
If your host application uses the GSM_SYNC pin to control a status LED as described in
Chapter 3.12.2.2, please note that the LED is off while the GSM engine is in Alarm mode.
3.3.2 Turn off the GSM Part of XT55/56
To switch the module off the following procedures may be used:
• Normal shutdown procedure: Software controlled by sending the AT^SMSO command
over the serial application interface. See Chapter 3.3.2.1.
• Emergency shutdown: Hardware driven by switching the GSM_EMERGOFF line of the
board-to-board-connector to ground = immediate shutdown of supply voltages, only
applicable if the software controlled procedure fails! See Chapter 3.3.2.2.
• Automatic shutdown: See Chapter 3.3.3
a) Takes effect if undervoltage is detected.
b) Takes effect if XT55/56 board temperature exceeds critical limit.