User's Guide

UL865 Hardware User Guide

1VV0301050 Rev 2 – 2013-10-09

Signal

Function

I/O

RESET*

Phone reset

RESET* is used to reset the UL865. Whenever this signal is pulled low, the UL865 is reset.

When the device is reset it stops any operation. After the release of the reset UL865 is

unconditionally shut down, without doing any detach operation from the network where it is

registered. This behavior 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* is internally controlled on start-up to achieve a proper power-on reset sequence,

so there's no need to control this pin on start-up. It may only be used to reset a device already

on that is not responding to any command.

NOTE:

Do not use this signal to power OFF the UL865. Use the ON/OFF procedure to perform this

function.

Reset Signal Operating levels:

Signal

Min

Max

RESET* Input high

1.5V(NOTE1)

1.9V

RESET* Input low

0.35V

(NOTE1) 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.