atmega3250v-8auatmega325v-8ai ATMEL Corporation, atmega3250v-8auatmega325v-8ai Datasheet - Page 45

• Manufacturer Part Number: atmega3250v-8auatmega325v-8ai
• Description: Atmega3250 8-bit Microcontroller With In-system Programmable Flash
• Manufacturer: ATMEL Corporation

11.9
2570L–AVR–08/07
Timed Sequences for Changing the Configuration of the Watchdog Timer
Table 11-2.
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:
The sequence for changing configuration differs slightly between the two safety levels. Separate
procedures are described for each level.
WDP2
Assembly Code Example
C Code Example
0
0
0
0
1
1
1
1
WDT_off:
void WDT_off(void)
{
}
; Reset WDT
wdr
; Write logical one to WDCE and WDE
in
ori r16, (1<<WDCE)|(1<<WDE)
out WDTCR, r16
; Turn off WDT
ldi r16, (0<<WDE)
out WDTCR, r16
ret
/* Reset WDT */
__watchdog_reset();
/* Write logical one to WDCE and WDE */
WDTCR |= (1<<WDCE) | (1<<WDE);
/* Turn off WDT */
WDTCR = 0x00;
1. See
WDP1
0
0
1
1
0
0
1
1
r16, WDTCR
Watchdog Timer Prescale Select
“About Code Examples” on page
(1)
WDP0
0
1
0
1
0
1
0
1
(1)
Oscillator Cycles
Number of WDT
1,024K cycles
2,048K cycles
128K cycles
256K cycles
512K cycles
16K cycles
32K cycles
64K cycles
ATmega325/3250/645/6450
8.
Typical Time-out
at V
17.1 ms
34.3 ms
68.5 ms
0.14 s
0.27 s
0.55 s
CC
1.1 s
2.2 s
= 3.0V
Typical Time-out
at V
16.3 ms
32.5 ms
65 ms
0.13 s
0.26 s
0.52 s
CC
1.0 s
2.1 s
= 5.0V
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