User Manual

ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]

8271E–AVR–07/2012

Note: 1. See ”About Code Examples” on page 7.

Note: If the Watchdog is accidentally enabled, for example by a runaway pointer or brown-out condition, 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 situation, the application software should always clear the

Watchdog System Reset Flag (WDRF) and the WDE control bit in the initialization routine, even if the Watchdog is

not in use.

Assembly Code Example

(1)

WDT_off:

; Turn off global interrupt

cli

; Reset Watchdog Timer

wdr

; Clear WDRF in MCUSR

in r16, MCUSR

andi r16, (0xff & (0<<WDRF))

out MCUSR, r16

; Write logical one to WDCE and WDE

; Keep old prescaler setting to prevent unintentional time-out

lds 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

(1)

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();

}