Specifications

XT55 Hardware Interface Description
Confidential / Preliminary
s
mo b i l e
XT55_hd_v00.02 Page 35 of 116 17.03.2004
3.3.2.2 Maximum number of turn-on / turn-off cycles
Each time the module is shut down, data will be written from volatile memory to flash
memory. The guaranteed maximum number of write cycles is limited to 100.000.
3.3.2.3 Emergency shutdown using GSM_EMERGOFF pin
Caution: Use the GSM_EMERGOFF pin only when, due to serious problems, the
software is not responding for more than 5 seconds. Pulling the
GSM_EMERGOFF pin causes the loss of all information stored in the volatile
memory since power is cut off immediately. Therefore, this procedure is
intended only for use in case of emergency, e.g. if XT55 fails to shut down
properly.
The GSM_EMERGOFF signal is available on the board-to-board connector. To control the
GSM_EMERGOFF line it is recommended to use an open drain / collector driver. To turn the
GSM engine off, the GSM_EMERGOFF line has to be driven to ground for ³ 3.2s.
Figure 8: Deactivating GSM engine by GSM_EMERGOFF signal
GSM_BATT+
Internal reset
GSM_EMERGOFF
Controlled by external
application
max. 3.2s
GSM_IGT
GSM_VDD
How does it work:
· Voltage V
GSM_BATT+
is
permanently applied to the
module.
· The module is active while
the internal reset signal is
kept at high level.
During operation of XT55
the baseband controlle
r
generates watchdog pulses
at regular intervals.
Once the
GSM_EMERGOFF pin is
grounded these watchdog
pulses are cut off from the
power supply ASIC. The
power supply ASIC shuts
down the internal suppl
y
voltages of XT55 after max.
3.2s and the module turns
off. Consequently, the
output voltage at GSM_VDD
is switched off.
Controlled by
XT55 software