Siemens S55 Repair Documentation page 33

- Watchdog monitoring
As soon as the first Watchdog_µC pin rising is detected , the device start the
watchdog monitoring procedure. Standard switch off of the phone is the watchdog.
The first edge of watchdog is rising. If a falling edge is detected ass the first transient
the device will go to power down mode again and the whole phone is switched off.
Rising and falling edges must be detected alternated. With any edge on
Watchdog_µC pin a counter will be loaded. The next – compared to the previous edge
– inverted edge must occur between end of TA0,TA1 and end of TB0,TB1. If the
signal occurs before end of TA0, TA1 or is not detected until end of TB0, TB1, the
device will go to power down mode immediately after the violation of the WD criteria
occurs.
TA0, TA1 ~ 0.4 sec
TB0, TB1 ~ 3 sec
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