ST10R272L - WATCHDOG TIMER
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WATCHDOG TIMER
The Watchdog Timer is a fail-safe mechanisms which prevents the controller from
malfunctioning over a long period of time.
The Watchdog Timer is always enabled after a reset of the chip, and can only be disabled in
the time interval until the EINIT (end of initialization) instruction has been executed. Thus,
the chip’s start-up procedure is always monitored. The software has to be designed to
service the Watchdog Timer before it overflows. If, due to hardware or software related
failures, the software fails to do so, the Watchdog Timer overflows and generates an internal
hardware reset and pulls the RSTOUT pin low in order to allow external hardware
components to be reset.
The Watchdog Timer is a 16-bit timer, clocked with the system clock divided either by 2 or by
128. The high byte of the watchdog timer register can be set to a pre-specified reload value
(stored in WDTREL) in order to allow further variation of the monitored time interval. Each
time it is serviced by the application software, the high byte of the Watchdog Timer is
reloaded. The lower byte of the watchdog timer register is reset on each service access.
Figure 105 Watchdog timer block diagram
Figure 106 SFRs and port pins associated with the watchdog timer
WDTCON
RSTOUT
Reset Indication Pin
Data Registers
Control Registers
WDT