AT90S/LS4434 and AT90S/LS8535
47
Note:
The frequency of the Watchdog oscillator is voltage-dependent as shown in the Electrical Characteristics section.
The WDR (Watchdog Reset) instruction should always be executed before the Watchdog Timer is enabled. This ensures that
the reset period will be in accordance with the Watchdog Timer prescale settings. If the Watchdog Timer is enabled without
reset, the Watchdog Timer may not start to count from zero.
To avoid unintentional MCU resets, the Watchdog Timer should be disabled or reset before changing the Watchdog Timer
Prescale Select.
Table 22.
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
0
0
0
16K cycles
47 ms
15 ms
0
0
1
32K cycles
94 ms
30 ms
0
1
0
64K cycles
0.19 s
60 ms
0
1
1
128K cycles
0.38 s
0.12 s
1
0
0
256K cycles
0.75 s
0.24 s
1
0
1
512K cycles
1.5 s
0.49 s
1
1
0
1,024K cycles
3.0 s
0.97 s
1
1
1
2,048K cycles
6.0 s
1.9 s