SE867-AGPS User Guide
1VV0300860 Rev. 3 - 2010-05-10
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved
page 24 of 69
7.
Connection guidelines
7.1.
Reset
The active low reset signal must be pulled up to VDD_CTRL and controlled in order to
have the possibility to assert a reset at the start-up and in case of power fail. To
perform a correct reset control the use of a power-on-reset monitoring the 1V8_DIG
power supply is recommended, this will allow a correct reset assertion on both power-
up and power fail putting the module in the correct working configuration and
protecting it from damages. We also suggest providing a manual reset feature in order
to have the possibility to bypass the power-on-reset circuit in case of necessity. The
manual reset signal can be controlled either with a button or a GPIO coming from the
controller.
7.2.
WAKE1
WAKE1 is an input signal responsible for the module wake-up from sleep mode. The
wake-up functionality is performed simply driving this signal low, in order to avoid the
necessity of a GPIO dedicated to this signal it can be connected to the RX_UART so that
the module can be woken simply sending data on the RX_UART line. Attention to logic
levels compliance between the signals must be paid while connecting RX_UART with
WAKE1, indeed the two signals belong to different power islands and have different
reference voltages (V_IO for RX_UART and IOVDD_AIN for WAKE1, please refer to
paragraph 5.3 for logic levels details).
7.3.
PPS and RTC crystal
The PPS signal outputs a precise reference timing pulse with frequency 1Hz and length
100ms. For pulse voltage level please refers to paragraph 5.3.
The SE867-AGPS module requires an external 32.768 kHz crystal connected to RTC_IN
and RTC_OUT balls in order to generate the Real Time Clock. The suggested crystal
load capacitance and frequency tolerance are reported in the table below:
