User's Manual

XT55/56 Hardware Interface Description
Confidential / Released
s
XT55/56_hd_v02.06a Page 27 of 125 17.12.2004
Mode Function
POWER DOWN Normal shutdown after sending the AT^SMSO command.
The Power Supply ASIC (PSU-ASIC) disconnects the supply voltage from the
baseband part of the circuit. Only a voltage regulator in the PSU-ASIC is active
for powering the RTC. Software is not active. The serial interfaces are not
accessible.
Operating voltage (connected to GSM_BATT+) remains applied.
Alarm mode Restricted operation launched by RTC alert function while the module is in
POWER DOWN mode. Module will not be registered to GSM network. Limited
number of AT commands is accessible.
Charge-only mode Limited operation for battery powered applications. Enables charging while
module is detached from GSM network. Limited number of AT commands is
accessible. There are several ways to launch Charge-only mode:
• From POWER DOWN mode: Connect charger to the charger input pin of the
external charging circuit and the module’s GSM_POWER pin when XT55/56
was powered down by AT^SMSO.
• From Normal mode: Connect charger to the charger input pin of the external
charging circuit and the module’s GSM_POWER pin, then enter AT^SMSO.
Charge mode
during normal
operation
Normal operation (SLEEP, IDLE, TALK, GPRS IDLE, GPRS DATA) and
charging running in parallel. Charge mode changes to Charge-only mode when
the module is powered down before charging has been completed.
See Table 11 and Table 12 for the various options of waking up the GSM part of the XT55/56 module
and proceeding from one mode to another.