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CHAPTER 7 WATCHDOG TIMER
CHAPTER 7 WATCHDOG TIMER
7.1 Watchdog Timer Functions
The watchdog timer has the following functions.
• Watchdog timer
• Interval timer
Caution Select the watchdog timer mode or the interval timer mode with the watchdog timer mode register
(WDTM) (The watchdog timer and interval timer cannot be used at the same time).
(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.
Table 7-1. Watchdog Timer Overrun Detection Times
Runaway Detection Time MCS = 1 MCS = 0
2
11
× 1/fXX 2
11
× 1/fX (410
µ
s) 2
12
× 1/fX (819
µ
s)
2
12
× 1/fXX 2
12
× 1/fX (819
µ
s) 2
13
× 1/fX (1.64 ms)
2
13
× 1/fXX 2
13
× 1/fX (1.64 ms) 2
14
× 1/fX (3.28 ms)
2
14
× 1/fXX 2
14
× 1/fX (3.28 ms) 2
15
× 1/fX (6.55 ms)
2
15
× 1/fXX 2
15
× 1/fX (6.55 ms) 2
16
× 1/fX (13.1 ms)
2
16
× 1/fXX 2
16
× 1/fX (13.1 ms) 2
17
× 1/fX (26.2 ms)
2
17
× 1/fXX 2
17
× 1/fX (26.2 ms) 2
18
× 1/fX (52.4 ms)
2
19
× 1/fXX 2
19
× 1/fX (104.9 ms) 2
20
× 1/fX (209.7 ms)
Remarks 1. f
XX : Main system clock frequency (fX or fX/2)
2. f
X : Main system clock oscillation frequency
3. MCS : Oscillation mode selection register (OSMS) bit 0
4. Values in parentheses when operated at f
X = 5.0 MHz.