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CHAPTER 10 WATCHDOG TIMER FUNCTION
User’s Manual U15109EJ3V0UD
317
(1) Watchdog timer mode
This mode detects an inadvertent program loop. When a loop is detected, a non-maskable interrupt can be
generated.
Table 10-1. Loop Detection Time of Watchdog Timer
Loop Detection Time
Clock
f
XX
= 20 MHz
f
XX
= 18.87 MHz
f
XX
= 16 MHz
2
16
/f
XX
3.3 ms
3.5 ms
4.1 ms
2
17
/f
XX
6.6 ms
6.9 ms
8.2 ms
2
18
/f
XX
13.1 ms
13.9 ms
16.4 ms
2
19
/f
XX
26.2 ms
27.8 ms
32.8 ms
2
20
/f
XX
52.4 ms
55.6 ms
65.5 ms
2
21
/f
XX
104.9 ms
111.1 ms
131.1 ms
2
22
/f
XX
209.7 ms
222.3 ms
262.1 ms
2
24
/f
XX
838.9 ms
889.1 ms
1.05 s
(2) Interval timer mode
Interrupts are generated at a preset time interval.
Table 10-2. Interval Time of Interval Timer
Interval Time
Clock
f
XX
= 20 MHz
f
XX
= 18.87 MHz
f
XX
= 16 MHz
2
16
/f
XX
3.3 ms
3.5 ms
4.1 ms
2
17
/f
XX
6.6 ms
6.9 ms
8.2 ms
2
18
/f
XX
13.1 ms
13.9 ms
16.4 ms
2
19
/f
XX
26.2 ms
27.8 ms
32.8 ms
2
20
/f
XX
52.4 ms
55.6 ms
65.5 ms
2
21
/f
XX
104.9 ms
111.1 ms
131.1 ms
2
22
/f
XX
209.7 ms
222.3 ms
262.1 ms
2
24
/f
XX
838.9 ms
889.1 ms
1.05 s