U5021M データシートの表示（PDF） - Atmel Corporation

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U5021M

Digital Window Watchdog Timer

Atmel Corporation 

Figure 4-4. Pulse Diagram of a Correct Trigger Sequence During the Short Watchdog Time

VDD

Reset out

Mode

t0

t1

t2

t3

t2

Trigger

Pin 6

Pin 5

Pin 3

Pin 2

Enable

ttrig

Pin 4

Figure 4-5 shows the switch-over from the short to the long watchdog mode. The wake-up signal

during the enable time, t5, activates a reset pulse, t6.

The watchdog can be switched back from the long to the short watchdog mode with a low poten-

tial at the mode pin (pin 3).

Figure 4-5. Pulse Diagram of the Long Watchdog Time

Reset out

Wake-up

t4

Mode

t2

Trigger

Enable

t6 t1

Pin 5

Pins 1

t5

Pin 3

Pin 2

Pin 4

5. State Diagram

The kernel of the watchdog is a finite state machine. Figure 5-1 shows the state diagram with all

possible states and transmissions. Many transmissions are controlled by an internal timer. The

numbers for the time-outs are the same as on the pulse diagrams.

6 U5021M

4756D–AUTO–11/05

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