Precautions When Using Watchdog Timer - Fujitsu F2MC-8FX Hardware Manual

CHAPTER 11 WATCHDOG TIMER
11.5

Precautions when Using Watchdog Timer

Care must be taken for the following points when using the watchdog timer.
Precautions when Using Watchdog Timer
Stopping the watchdog timer
Once activated, the watchdog timer cannot be stopped until a reset is generated.
Selecting the count clock
The count clock switch bits (WDTC:CS1,0) can be rewritten only when the watchdog control bits
(WDTC:WTE3 to WTE0) are set to "0101
switch bits cannot be written by a bit operation instruction. Moreover, the bit settings should not be
changed once the timer is activated.
In the subclock mode, the timebase timer does not operate because the main clock stops oscillating.
In order to operate the watchdog timer in the subclock mode, it is necessary to select the watch prescaler as
the count clock beforehand and set "WDTC:CS1,0" to "10
Clearing the watchdog timer
Clearing the counter used for the count clock of the watchdog timer (timebase timer or watch prescaler)
also clears the counter of the watchdog timer.
The counter of the watchdog timer is cleared when entering the sleep mode, stop mode or watch mode.
Programming precaution
When creating a program in which the watchdog timer is cleared repeatedly in the main loop, set the
processing time of the main loop including the interrupt processing time to the minimum watchdog timer
interval time or shorter.
180
" upon the activation of the watchdog timer. The count clock
B
" or "11 ".
B B