Cinterion MC55i - Automatic Thermal Shutdown; Disconnecting Power Supply; Rtc

MC55i Terminal Hardware Interface Description
3.5 Power Supply
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MC55i_Terminal_HD_v01.201a Page 24 of 47 2010-04-16
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When the MC55i Terminal enters the POWER DOWN mode, e.g. after you have issued the
AT^SMSO command or activated the PD_IN signal, all RS-232 interface lines are active for a
period of 50ms to max. 3.5s. This may cause undefined characters to be transmitted on the
RS-232 lines which can be ignored.
3.5.4 Disconnecting power supply
Before disconnecting the power supply from the PLUS pin, make sure that the MC55i Terminal
is in a safe condition. The best way is to wait 1s after the "^SHUTDOWN" result code has been
indicated.
3.5.5 Automatic thermal shutdown
An on-board NTC measures the temperature of the built-in MC55i module. If over- or under-
temperature is detected on the module the MC55i Terminal automatically shuts down to avoid
thermal damage to the system. Table 15 specifies the ambient temperature threshold for the
MC55i Terminal.
The automatic shutdown procedure is equivalent to the power-down initiated with the AT^SM-
SO command, i.e. MC55i Terminal logs off from the network and the software enters a secure
state avoiding loss of data. In IDLE mode it takes typically one minute to deregister from the
network and to switch off.
Alert messages transmitted before the MC55i Terminal switches off are implemented as Unso-
licited Result codes (URCs). For details see the description of AT^SCTM command provided
in [1].
Thermal shutdown will be deferred if a critical temperature limit is exceeded, while an emer-
gency call or a call to a predefined phone number is in progress, or during a two minute guard
period after power up. See [1] for details.
3.5.6 RTC
The internal Real Time Clock (RTC) of the MC55i Terminal retains the time and date and han-
dles the alarm (reminder) function. The AT+CCLK command serves to set the time and date,
and AT+CALA specifies a reminder message. See [1] for details.
A dedicated voltage regulator backs up the RTC even in POWER DOWN mode and enables
MC55i Terminal to keep track of time and date.
However, please note that the Alarm mode described in [1], Section AT+CALA, is not intended
for the MC55i Terminal. The AT+CALA command can only be used to set a reminder message,
but not to configure the mobile to wake up from POWER DOWN mode into Alarm mode. There-
fore, after setting a timer with AT+CALA be sure not to shut down the MC55i Terminal by
AT^SMSO or PD_IN signal.