Datasheet
; reset WDT
WDR
; Write logical one to WDCE and WDE
in 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
void WDT_off(void)
{
/* reset WDT */
_WDR();
/* Write logical one to WDCE and WDE */
WDTCR |= (1<<WDCE) | (1<<WDE);
/* Turn off WDT */
WDTCR = 0x00;
}
15.5.1 Safety Level 1 (WDTON Fuse Unprogrammed)
In this mode, the Watchdog Timer is initially disabled, but can be enabled by writing the WDE bit to 1
without any restriction. A timed sequence is needed when changing the Watchdog Time-out period or
disabling an enabled Watchdog Timer. To disable an enabled Watchdog Timer and/or changing the
Watchdog Time-out, the following procedure must be followed:
1. In the same operation, write a logic one to WDCE and WDE. A logic one must be written to WDE
regardless of the previous value of the WDE bit.
2. Within the next four clock cycles, in the same operation, write the WDE and WDP bits as desired,
but with the WDCE bit cleared.
15.5.2 Safety Level 2 (WDTON Fuse Programmed)
In this mode, the Watchdog Timer is always enabled, and the WDE bit will always read as one. A timed
sequence is needed when changing the Watchdog Time-out period. To change the Watchdog Time-out,
the following procedure must be followed:
1. In the same operation, write a logical one to WDCE and WDE. Even though the WDE always is set,
the WDE must be written to one to start the timed sequence.
Within the next four clock cycles, in the same operation, write the WDP bits as desired, but with the
WDCE bit cleared. The value written to the WDE bit is irrelevant.
15.6 Register Description
AVR 8-Bit Microcontroller
System Control and Reset
© 2017 Microchip Technology Inc.
Datasheet Complete
40001974A-page 64