User Manual

Table Of Contents
XT55/56 Hardware Interface Description
Confidential / Preliminary
s
XT55/56_hd_v02.96 Page 32 of 125 18.08.2005
3.3.1.1 Turn on the GSM Part of XT55/56 Using the Ignition Line GSM_IGT
(Power on)
To switch on the XT55/56 GSM part the GSM_IGT (Ignition) signal needs to be driven to
ground level for at least 100ms and not earlier than 10ms after the last falling edge of
GSM_VDD. This can be accomplished using an open drain/collector driver in order to avoid
current flowing into this pin.
Software
controlled
GSM_EMERGOFF
ca. 300ms ca. 900ms
Serial interfaces
ASC0 and ASC1
Undefined
Inactive
Active
GSM_VDD
ca. 60ms
GSM_TXD0
GSM_TXD1
GSM_DSR0
GSM_BATT+
GSM_IGT
min. 10ms
min.
100ms
HiZ
HiZ
Figure 4: Power-on by ignition signal
In a battery operated XT55/56 application, the duration of the GSM_IGT signal must be 1s
minimum when the charger is connected and you may want to go from Charge only mode to
Normal mode.
For details
p
lease see Cha
p
ter 3.3.1.2