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NEC PD78055 Manuale Utente

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CHAPTER 11  WATCHDOG TIMER
11.1  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 (runaway) is detected.  Upon detection of the runaway, a non-maskable interrupt
request or RESET can be generated.
Table 11-1.  Watchdog Timer Runaway Detection Times
Runaway Detection Time
MCS = 1
MCS = 0
2
11
 
×
 1/f
XX
2
11
 
×
 1/f
X
 (410 
µ
s)
2
12
 
×
 1/f
X
 (819 
µ
s)
2
12
 
×
 1/f
XX
2
12
 
×
 1/f
X
 (819 
µ
s)
2
13
 
×
 1/f
X
 (1.64 ms)
2
13
 
×
 1/f
XX
2
13
 
×
 1/f
X
 (1.64 ms)
2
14
 
×
 1/f
X
 (3.28 ms)
2
14
 
×
 1/f
XX
2
14
 
×
 1/f
X
 (3.28 ms)
2
15
 
×
 1/f
X
 (6.55 ms)
2
15
 
×
 1/f
XX
2
15
 
×
 1/f
X
 (6.55 ms)
2
16
 
×
 1/f
X
 (13.1 ms)
2
16
 
×
 1/f
XX
2
16
 
×
 1/f
X
 (13.1 ms)
2
17
 
×
 1/f
X
 (26.2 ms)
2
17
 
×
 1/f
XX
2
17
 
×
 1/f
X
 (26.2 ms)
2
18
 
×
 1/f
X
 (52.4 ms)
2
19
 
×
 1/f
XX
2
19
 
×
 1/f
X
 (104.9 ms)
2
20
 
×
 1/f
X
 (209.7 ms)
Remarks 1. f
XX
:  Main system clock frequency (f
X
 or f
X
/2)
2. f
X
:  Main system clock oscillation frequency
3. MCS :  Bit 0 of oscillation mode selection register (OSMS)
4. Figures in parentheses apply to operation with f
X
 = 5.0 MHz.