User's Manual

DE910 Series Hardware User Guide
1vv0301183 Rev.1 – 2015-2-13
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved. Page 24 of 70
TIP:
To check if the device has powered off, hardware line PWRMON must be monitored. When
PWRMON goes low, the device has powered off.
4.3. Hardware Reset
WARNING:
The Hardware Reset must not be used during normal operation of the device since it does not
detach the device from the network. It shall be kept as an emergency exit procedure to be
done in the rare case that the device gets stuck waiting for some network.
4.3.1. Hardware Reset
To Hardware reset the DE921, the pad RESIN* must be tied low for at least 45 microseconds
and then released.
A simple circuit to unconditionally shutdown the module is illustrated below:
NOTE:
Do not use any pull up resistor on the RESIN* line or any totem pole digital output. Using a
pull up resistor may bring latch up problems on the DE921 power regulator and result in
improper functioning of the module. The line RESIN* must be connected only in open
collector configuration.
TIP:
The unconditional hardware Shutdown must always be implemented on the boards and the
software must use it only as an emergency exit procedure.