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Startup
Activation of the PD_IN reset signal on
the power supply connection
The POWER DOWN line on the GSM/
GPRS module is connected to the
watchdog input pin of the power supply
ASIC, which can only be switched off
by changing the watchdog condition. To
do this, the PD_IN modem reset line is
active (high) for at least 3.5 s. This results
in immediate, “hard” disconnection, with
the modem unable to sign off correctly
from the base station in the STANDBY and
TALK operating states. In the case of this
hardware shutdown, the software is no
longer able to respond before the voltage
is switched off. This corresponds to a
direct, unannounced disconnection of the
operating voltage. In the application you
can switch off or reset the module without
interrupting the input voltage supply.
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