Cinterion
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ELS81-US Hardware Interface Description
2.1 Application Interface
53
els81-us_hid_v01.004
2017-09-27
Confidential / Preliminary
Page 41 of 107
2.1.13.4
Fast Shutdown
The GPIO4 interface line can be configured as fast shutdown signal line FST_SHDN. The con-
figured FST_SHDN line is an active low control signal and must be applied for at least 1 milli-
seconds. If unused this line can be left open because of a configured internal pull-up resistor.
Before setting the FST_SHDN line to low, the ON signal should be set to low (see
).
Otherwise there might be back powering at the ON line in Power Down mode.
The fast shutdown feature can be triggered using the AT command AT^SMSO=<fso>. For de-
tails see
If triggered, a low impulse >1 milliseconds on the FST_SHDN line starts the fast shutdown. The
fast shutdown procedure still finishes any data activities on the module's flash file system, thus
ensuring data integrity, but will no longer deregister gracefully from the network, thus saving
the time required for network deregistration.
Figure 19:
Fast shutdown timing
Please note that the normal software controlled shutdown using AT^SMSO will allow option for
a fast shutdown by parameter <fso>, i.e., without network deregistration. However, in this case
no URCs including shutdown URCs will be provided by the AT^SMSO command.
Please also note that the fast shutdown operation does not allow the module deregister from
the network, therefore, this practice is not recommended, and should not be conducted on reg-
ular basis. If it is used for energy saving reason, for instance, used in battery-driven solutions
that require prompt system shutdown before battery depletion, discretion is advised in such
case.
BATT+
VCORE
V180
VDDLP
Fast shut down procedure
Power down
EMERG_RST
ON
GPIO4/FST_SHDN
<15ms
_
