
56
8272E–AVR–04/2013
ATmega164A/PA/324A/PA/644A/PA/1284/P
1.
In the same operation, write a logic one to the Watchdog change enable bit (WDCE) and
WDE. A logic one must be written to WDE regardless of the previous value of the WDE
bit.
2.
Within the next four clock cycles, write the WDE and Watchdog prescaler bits (WDP) as
desired, but with the WDCE bit cleared. This must be done in one operation.
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 (for example, by disabling
interrupts globally) so that no interrupts will occur during the execution of these functions.
Notes:
1. The example code assumes that the part specific header file is included.
Assembly Code Example
WDT_off:
; Turn off global interrupt
cli
; Reset Watchdog Timer
wdr
; Clear WDRF in MCUSR
in
r16, MCUSR
andi
r16, ~(1<<WDRF)
out
MCUSR, r16
; Write logical one to WDCE and WDE
; Keep old prescaler setting to prevent unintentional time-out
ldi
r16, WDTCSR
ori
r16, (1<<WDCE) | (1<<WDE)
sts
WDTCSR, r16
; Turn off WDT
ldi
r16, (0<<WDE)
sts
WDTCSR, 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 */
WDTCSR |= (1<<WDCE) | (1<<WDE);
/* Turn off WDT */
WDTCSR = 0x00;
__enable_interrupt();
}