ATtiny13A datasheet(41/174 Pages) ATMEL

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8126D–AVR–11/09

ATtiny13A

tion, the application software should always clear the Watchdog System Reset Flag (WDRF)

and the WDE control bit in the initialisation routine, even if the Watchdog is not in use.

The following code example shows one assembly and one C function for changing the time-out

value of the Watchdog Timer.

Note:

See “Code Examples” on page 6.

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.

Assembly Code Example

WDT_Prescaler_Change:

; Turn off global interrupt

cli

; Reset Watchdog Timer

wdr

; Start timed sequence

r16, WDTCR

ori

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

out

WDTCR, 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)

out

WDTCR, 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 */

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

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

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

__enable_interrupt();

}

ATtiny13A 数据表(PDF) 41 Page - ATMEL Corporation

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