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10.1 Watch Timer Functions
The watch timer has the following functions.
• Watch timer
• Interval timer
The watch timer and the interval timer can be used simultaneously.
(1) Watch timer
When the 32.768 kHz subsystem clock is used, a flag (WTIF) is set at 0.5 second or 0.25 second intervals.
When the 8.38 MHz main system clock is used, a flag (WTIF) is set at 0.5 second or 0.25 second intervals.
In addition, when the 4.19 MHz (Standard: 4.194304 MHz) main system clock is used, a flag (WTIF) is set at
0.5 second or 1 second intervals.
When a frequency other than above is used, a flag (WTIF) is not set at 0.5/0.25 or 0.5/1.0 intervals.
Caution When 8.38 MHz or 4.19 MHz frequency is used, a time interval has a little error.
(2) Interval timer
Interrupt requests (INTTM3) are generated at the preset time interval.
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Interval Time
× 1/f
4
2
W
× 1/f
2
5
W
× 1/f
6
2
W
× 1/f
2
7
W
× 1/f
2
8
W
× 1/f
9
2
W
Remarks f
Table 10-1. Interval Timer Interval Time
When operated
at f
= 10.0 MHz
X
409.6 µ s
819.2 µ s
1.64 ms
3.28 ms
6.55 ms
13.1 ms
: Main system clock oscillation frequency
X
f
: Subsystem clock oscillation frequency
XT
f
: Watch timer clock frequency (f
W
CHAPTER 10 WATCH TIMER
CHAPTER 10 WATCH TIMER
When operated at
f
= 8.38 MHz
X
489 µ s
978 µ s
1.96 ms
3.91 ms
7.82 ms
15.6 ms
8
/2
or f
)
X
XT
When operated at
When operated at
f
= 4.19 MHz
f
X
XT
978 µ s
488 µ s
977 µ s
1.96 ms
3.91 ms
1.95 ms
7.82 ms
3.91 ms
15.6 ms
7.81 ms
31.3 ms
15.6 ms
= 32.768 kHz
223
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