ATtiny13A datasheet(40/174 Pages) ATMEL

40 / 174 page

8126D–AVR–11/09

ATtiny13A

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 (e.g. by disabling interrupts

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

Note:

See “Code Examples” on page 6.

If the Watchdog is accidentally enabled, for example by a runaway pointer or brown-out condi-

tion, 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 situa-

Assembly Code Example

WDT_off:

; Turn off global interrupt

cli

; Reset Watchdog Timer

wdr

; Clear WDRF in MCUSR

r16, MCUSR

andi

r16, (0xff - (1<<WDRF))

out

MCUSR, r16

; Write logical one to WDCE and WDE

; Keep old prescaler setting to prevent unintentional time-out

r16, WDTCR

ori

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

out

WDTCR, r16

; Turn off WDT

ldi

r16, (0<<WDE)

out

WDTCR, 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 */

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

/* Turn off WDT */

WDTCR = 0x00;

__enable_interrupt();

}

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