Datasheet

The following code examples shows how to change the time-out value of the Watchdog

Timer.

Assembly Code Example

WDT_Prescaler_Change:

; Turn off global interrupt

cli

; Reset Watchdog Timer

wdr

; Start timed sequence

lds r16, WDTCSR

ori r16, (1<<WDCE) | (1<<WDE)

sts WDTCSR, r16

; -- Got four cycles to set the new values from here -

; Set new prescaler(time-out) value = 64K cycles (~0.5 s)

ldi r16, (1<<WDE) | (1<<WDP2) | (1<<WDP0)

sts WDTCSR, r16

; -- Finished setting new values, used 2 cycles -

; Turn on global interrupt

sei

ret

C Code Example

void WDT_Prescaler_Change(void)

{

__disable_interrupt();

__watchdog_reset();

/* Start timed sequence */

WDTCSR |= (1<<WDCE) | (1<<WDE);

/* Set new prescaler(time-out) value = 64K cycles (~0.5 s) */

WDTCSR = (1<<WDE) | (1<<WDP2) | (1<<WDP0);

__enable_interrupt();

}

Note: The Watchdog Timer should be reset before any change of the WDTCSR.WDP

bits, since a change in the WDTCSR.WDP bits can result in a time-out when switching to

a shorter time-out period.

11.9. Register Description

Atmel ATmega16M1/32M1/64M1 [DATASHEET]

Atmel-8209F-ATmega16M1/32M1/64M1_Datasheet_Complete-10/2016