Precautions When Using Watch Prescaler - Fujitsu F2MC-8FX Hardware Manual

CHAPTER 13 WATCH PRESCALER
13.6

Precautions when Using Watch Prescaler

Shown below are the precautions that must be followed when using the watch
prescaler.
The watch prescaler cannot be used in single system clock option product.
Precautions when Using Watch Prescaler
When setting the prescaler by program
The prescaler cannot be recovered from interrupt processing when the watch interrupt request flag bit
(WPCR:WTIF) is set to "1" and the interrupt request enable bit is enabled (WPCR:WTIE = 1). Always
clear the WTIF bit within the interrupt routine.
Clearing the watch prescaler
When the watch prescaler is selected as the count clock of the watchdog timer (WDTC:CS1, 0 = 10 or CS1,
0 = 11), clearing the watch prescaler also clears the watchdog timer.
Watch interrupts
In the main stop mode, the watch prescaler performs counting but does not generate the watch prescaler
interrupts (IRQ20).
Peripheral functions receiving clock from the watch prescaler
If the watch prescaler is cleared when the output of the watch prescaler is used in other peripheral
functions, this will affect the operation by changing the count time or in other manners.
The clock for the watchdog timer is also outputted from the initial state. However, as the watchdog timer
counter is cleared at the same time as the prescaler counter, the watchdog timer operates in the normal
cycles.
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