ATMEGA88V_14 Datasheet, PDF (52/377 Pages) ATMEL Corporation – High endurance non-volatile memory segments

ATmega48/88/168
The following code example shows one assembly and one C function for changing the time-out
value of the watchdog timer.
Assembly code example⁽¹⁾
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⁽¹⁾
void WDT_Prescaler_Change(void)
{
__disable_interrupt();
__watchdog_reset();
/* Start timed equence */
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: 1. See ”About code examples” on page 8.
Note: The watchdog timer should be reset before any change of the WDP bits, since a change in
the WDP bits can result in a time-out when switching to a shorter time-out period.
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2545T–AVR–05/11