Rainbow Electronics ATtiny28L - Manual (Page 27)

27
ATtiny28L/V
1062E–10/01
• Bits 2..0 – WDP2, WDP1, WDP0: Watchdog Timer Prescaler 2, 1 and 0
The WDP2, WDP1 and WDP0 bits determine the Watchdog Timer prescaling when the
Watchdog Timer is enabled. The different prescaling values and their corresponding
time-out periods are shown in Table 11.
Note: The frequency of the Watchdog oscillator is voltage-dependent, as shown in the section
“Typical Characteristics” on page 55.
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 counting from zero.
Table 11. Watchdog Timer Prescale Select
WDP2 WDP1 WDP0
Number of WDT
Oscillator
Cycles Typical
Time-out at
V
CC
= 2.0V
Typical
Time-out at
V
CC
= 3.0V
Typical
Time-out at
V
CC
= 5.0V
0 0 0 16K cycles 0.15 s 47 ms 15 ms
0 0 1 32K cycles 0.30 s 94 ms 30 ms
0 1 0 64K cycles 0.60 s 0.19 s 60 ms
0 1 1 128K cycles 1.2 s 0.38 s 0.12 s
1 0 0 256K cycles 2.4 s 0.75 s 0.24 s
1 0 1 512K cycles 4.8 s 1.5 s 0.49 s
1 1 0 1,024K cycles 9.6 s 3.0 s 0.97 s
1 1 1 2,048K cycles 19 s 6.0 s 1.9 s