User's Guide

HE863 Family Hardware User Guide
1vv0300891 Rev.5
- 2011-03-18
Reproduction forbidden without Telit Communications S.p.A’s. written authorization - All Rights
Reserved. Page 33 of 89
iii. Using ON/OFF key when USB interface is used
If the application will use the usb interface of HE863 Family,
that is, actually the usb interface is correctly connected
between the devices and USB_VBUS is asserted, the hold time to
tie ON/OFF# to GND should be 3 ~ 4 sec to make it powering on.
During the Initialization state, any kind of AT-command is not
available. DTE must be waiting for the Activation state to
communicate with HE863 Family.
NOTE:
To check if the HE863 Family has powered on, the hardware line
PWRMON must be monitored. When PWRMON goes high, the module
has powered on.
NOTE:
Do not use any pull up resistor on the ON/OFF# line, it is
internally pulled up. Using pull up resistor may bring to
latch up problems on the HE863 Family power regulator and
improper power on/off of the module. The line ON# must be
connected only in open collector configuration.
NOTE:
In this document all the lines are inverted. Active low
signals are labeled with a name that ends with a "#" or with a
bar over the name.