at90ls4433 ATMEL Corporation, at90ls4433 Datasheet - Page 44

• Manufacturer Part Number: at90ls4433
• Description: At90s4433 8-bit Avr Microcontroller With 4k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

44
AT90S/LS4433
• 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 inTable 16.
Table 16. Watchdog Timer Prescale Select
Note:
WDP2
0
0
0
0
1
1
1
1
1. The frequency of the Watchdog Oscillator is voltage dependent, as shown in the
WDP1
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 counting from zero.
To avoid unintentional MCU reset, the Watchdog Timer should be disabled or Reset
before changing the Watchdog Timer Prescale Select.
0
0
1
1
0
0
1
1
WDP0
0
1
0
1
0
1
0
1
Oscillator Cycles
Number of WDT
1,024K cycles
2,048K cycles
128K cycles
256K cycles
512K cycles
16K cycles
32K cycles
64K cycles
(1)
Typical Time-out
at V
47 ms
94 ms
0.19 s
0.38 s
0.75 s
CC
1.5 s
3.0 s
6.0 s
= 3.0V
Typical Time-out
at V
1042H–AVR–04/03
15 ms
30 ms
60 ms
0.12 s
0.24 s
0.49 s
0.97 s
CC
1.9 s
= 5.0V