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LTE Terminals Hardware Interface Description
3.10 Automatic thermal shutdown
47
ELSxT_HID_v04 2018-09-04
Confidential / Preliminary
Page 44 of 102
3.10 Automatic thermal shutdown
An on-board NTC measures the temperature of the built-in LTE module. If over- or under-tem-
perature is detected on the module the LTE Terminals automatically shut down to avoid thermal
damage to the system. Table 25 specifies the ambient temperature threshold for the LTE Ter-
minals.
The automatic shutdown procedure is equivalent to the power-down initiated with the AT^SM-
SO command, i.e. LTE Terminals log off from the network and the software enters a secure
state avoiding loss of data.
Alert messages transmitted before the LTE Terminals switch off are implemented as Unsolic-
ited Result codes (URCs). For details see the description of AT^SCTM command provided in
[1].
The watchdog can be configured to restart the LTE Terminals after a defined period of time.
3.11 Hardware Watchdog
The LTE Terminals feature a programmable hardware watchdog that permanently monitors the
terminals hardware and can be configured to react to various hardware states. The watchdog
may for example be configured to periodically restart the terminal, independent of its current
operating state. Figure 6 shows how the watchdog is integrated into the LTE Terminals.
Please refer to Chapter 8 for details on how to control and configure the hardware watchdog.
3.12 RTC
The internal Real Time Clock (RTC) of the LTE Terminals retains the time and date and han-
dles the alarm function. The AT+CCLK command serves to set the time and date, and AT+CA-
LA specifies a reminder message or sets an alarm for the LTE Terminals to wake up. See [1]
for details.
A dedicated voltage regulator backs up the RTC even in Power Down mode and enables LTE
Terminals to keep track of time and date.
However, please note that the Alarm function described in [1], Section AT+CALA, will only work
if Always On is not configured (see Section 8.3.1.8). Otherwise, the AT+CALA command can
only be used to set a reminder message, but not to configure the LTE Terminals to wake up
from Power Down mode.
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