Notes On Using Watch Prescaler - Fujitsu 8FX Hardware Manual

CHAPTER 9 WATCH PRESCALER

9.6 Notes on Using Watch Prescaler

9.6 Notes on Using Watch Prescaler
This section provides notes on using the watch prescaler.
■ Notes on Using Watch Prescaler
● When setting interrupt processing in a program
The watch prescaler cannot be waken up from interrupt processing if the watch prescaler
interrupt request flag bit (WPCR:WTIF) is set to "1" and the interrupt request is enabled
(WPCR:WTIE = 1). Always clear the WTIF bit in the interrupt routine.
● Clearing the watch prescaler
When the watch prescaler is selected as the count clock of the software watchdog timer
(WDTC:CS[1:0], CSP = 0b100 or 0b110), clearing the watch prescaler also clears the software
watchdog timer.
● Watch prescaler interrupts
In stop mode in which the main clock, the main CR clock, or the main CR PLL clock is used,
the watch prescaler performs counting, and can generate the watch prescaler interrupt.
● Peripheral functions receiving clock from the watch prescaler
If the counter of the watch prescaler is cleared when the output of the watch prescaler is used in
other peripheral functions, the operations of such peripheral functions may be affected such as
the changing of their operating cycles.
After the counter of the watch prescaler is cleared, the clock for the software watchdog timer
output from the watch prescaler returns to the initial state. However, since the software
watchdog timer counter is also cleared at the same time as the clock for the software watchdog
timer returns to the initial state, the software watchdog timer operates in its normal cycle.
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MB95630H Series
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