User Guide

HE910 Hardware User Guide

1vv0300925 Rev.18 – 15-06-2012

The HE910 module is provided by two Reset lines that are described in the following table:

Signal

Function

I/O

PAD

HW_SHUTDOWN*

Phone Unconditional

Shut Down

R13

Unconditional Shutdown of the module.

It will NOT perform the detach from the

cellular network

RESET*

Phone reset

P11

Power-cycle of the module, but will NOT

perform the detach from the cellular network

RESET* and HW_SHUTDOWN are used to reset the HE910. Whenever those signals are

pulled low, the HE910 is reset. When the device is reset it stops any operation. After the

release of the reset HE910 is unconditionally shut down (in case of HW_SHUTDOWN*) or

restart (in case of RESET*), without doing any detach operation from the network where it

is registered. This behaviour is not a proper shut down because any GSM device is requested

to issue a detach request on turn off. For this reason the Reset signal must not be used to

normally shutting down the device, but only as an emergency exit in the rare case the device

remains stuck waiting for some network response.

The RESET* and HW_SHUTDOWN* are internally controlled on start-up to achieve always

a proper power-on reset sequence, so there's no need to control the pins on start-up. They

may only be used to reset a device already on that is not responding to any command.

NOTE:

Do not use those signals to power off the HE910. Use the ON/OFF signal to perform this

function or the AT#SHDN command.

Reset Signal Operating levels:

Signal

Min

Max

Input high

1.5V

1.9V

Input low

0.35V

* this signal is internally pulled up so the pin can be left floating if not used.

If unused, this signal may be left unconnected. If used, then it must always be connected

with an open collector transistor, to permit to the internal circuitry the power on reset and

under voltage lockout functions.