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40
8126F–AVR–05/12
ATtiny13A
The following code example shows one assembly and one C function for turning off the Watch-
dog Timer. The example assumes that interrupts are controlled (e.g. by disabling interrupts
globally) so that no interrupts will occur during the execution of these functions.
Note:
See
.
If the Watchdog is accidentally enabled, for example by a runaway pointer or brown-out condi-
tion, the device will be reset and the Watchdog Timer will stay enabled. If the code is not set up
to handle the Watchdog, this might lead to an eternal loop of time-out resets. To avoid this situa-
Assembly Code Example
WDT_off:
; Turn off global interrupt
cli
; Reset Watchdog Timer
wdr
; Clear WDRF in MCUSR
in
r16, MCUSR
andi
r16, (0xff - (1<<WDRF))
out
MCUSR, r16
; Write logical one to WDCE and WDE
; Keep old prescaler setting to prevent unintentional time-out
in
r16, WDTCR
ori
r16, (1<<WDCE) | (1<<WDE)
out
WDTCR, r16
; Turn off WDT
ldi
r16, (0<<WDE)
out
WDTCR, r16
; Turn on global interrupt
sei
ret
C Code Example
void WDT_off(void)
{
__disable_interrupt();
__watchdog_reset();
/* Clear WDRF in MCUSR */
MCUSR &= ~(1<<WDRF);
/* Write logical one to WDCE and WDE */
/* Keep old prescaler setting to prevent unintentional time-out */
WDTCR |= (1<<WDCE) | (1<<WDE);
/* Turn off WDT */
WDTCR = 0x00;
__enable_interrupt();
}