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11.1 Watchdog Timer Functions
The watchdog timer has the following functions.
• Watchdog timer
• Interval timer
Caution
(1) Watchdog timer mode
An inadvertent program loop is detected. Upon detection of the inadvertent program loop, a non-maskable
interrupt request or RESET can be generated.
Inadvertent Program Loop
Detection Time
× 1/f
2
12
× 1/f
13
2
× 1/f
2
14
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× 1/f
2
15
Remark
(2) Interval timer mode
Interrupt requests are generated at the preset time intervals.
Interval Time
× 1/f
2
12
× 1/f
2
13
× 1/f
14
2
× 1/f
2
15
Remark
Select the watchdog timer mode or the interval timer mode with the watchdog timer mode register
(WDTM) (the watchdog timer and the interval timer cannot be used simultaneously).
Table 11-1. Watchdog Timer Inadvertent Program Loop Detection Time
When operated at
409.6 µ s
X
819.2 µ s
X
1.64 ms
X
3.28 ms
X
f
: Main system clock oscillation frequency
X
When operated at
409.6 µ s
X
819.2 µ s
X
1.64 ms
X
3.28 ms
X
f
: Main system clock oscillation frequency
X
CHAPTER 11 WATCHDOG TIMER
CHAPTER 11 WATCHDOG TIMER
Inadvertent Program Loop
f
= 10.0 MHz
X
× 1/f
2
16
× 1/f
17
2
× 1/f
2
18
× 1/f
2
20
Table 11-2. Interval Time
f
= 10.0 MHz
X
× 1/f
2
16
× 1/f
2
17
× 1/f
18
2
× 1/f
2
20
When operated at
Detection Time
6.55 µ s
X
13.1 µ s
X
26.2 ms
X
104.9 ms
X
Interval Time
When operated at
6.55 ms
X
13.1 ms
X
26.2 ms
X
104.9 ms
X
f
= 10.0 MHz
X
f
= 10.0 MHz
X
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