ATMEGA325 datasheet(46/353 Pages) ATMEL

46 / 353 page

ATmega325/3250/645/6450

2570J–AVR–11/06

The following code example shows one assembly and one C function for turning off the

WDT. The example assumes that interrupts are controlled (e.g. by disabling interrupts

globally) so that no interrupts will occur during execution of these functions.

Note:

1. See “About Code Examples” on page 8.

Table 21. Watchdog Timer Prescale Select

WDP2

WDP1

WDP0

Number of WDT

Oscillator Cycles

Typical Time-out

at V

CC = 3.0V

Typical Time-out

at V

CC = 5.0V

16K cycles

17.1 ms

16.3 ms

32K cycles

34.3 ms

32.5 ms

64K cycles

68.5 ms

65 ms

128K cycles

0.14 s

0.13 s

256K cycles

0.27 s

0.26 s

512K cycles

0.55 s

0.52 s

1,024K cycles

1.1 s

1.0 s

2,048K cycles

2.2 s

2.1 s

Assembly Code Example(1)

WDT_off:

; Reset WDT

wdr

; Write logical one to WDCE and WDE

r16, WDTCR

ori

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

out

WDTCR, r16

; Turn off WDT

ldi

r16, (0<<WDE)

out

WDTCR, r16

ret

C Code Example(1)

void

WDT_off(void)

{

/* Reset WDT */

__watchdog_reset();

/* Write logical one to WDCE and WDE */

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

/* Turn off WDT */

WDTCR = 0x00;

}

ATMEGA325 Datasheet(PDF) 46 Page - ATMEL Corporation

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