Rainbow-electronics AT90LS4433 Manual do Utilizador descarregar pdf (Página 44)

AT90S/LS4433

1042G–AVR–09/02

• 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.

Note: 1. 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 counting from zero.

To avoid unintentional MCU reset, the Watchdog Timer should be disabled or Reset

before changing the Watchdog Timer Prescale Select.

Table 16. Watchdog Timer Prescale Select

(1)

WDP2 WDP1 WDP0

Number of WDT

Oscillator Cycles

Typical Time-out

at V

=3.0V

Typical Time-out

at V

=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

1 2 ... 39 40 41 42 43 44 45 46 47 48 49 ... 124 125

Sem comentários

Rainbow-electronics AT90LS4433 Manual do Utilizador Página 44