HE920 Hardware User Guide
1vv0301014 Rev.9 – 2014-01-23
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
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Page 25 of 84
4.
Hardware Commands
4.1.
Turning ON the HE920
To turn on HE920, the pad ON_OFF* must be tied low for at least 1 second and then released.
The maximum current that can be drained from the ON_OFF* pad is 0.1 mA.
A simple circuit to power on the module is illustrated below:
4.2.
Initialization and Activation state
Upon turning on HE920 module, The HE920 is not activated yet because the boot sequence of
HE920 is still going on internally. It takes about 10 seconds to complete the initializing the
module internally.
For this reason, it would be useless to try to access HE920 during the Initialization state as
below. To get the desirable stability, The HE920 needs at least 10 seconds after the
PWRMON goes High to become operational by reaching the activation state.
During the
Initialization state
, any kind of AT-command is not available. DTE must be
waiting for the
Activation state
to communicate with HE920.
