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(1)
Watch timer
The 4.19 MHz main system clock or 32.768 kHz subsystem clock is used to issue an interrupt request
(INTWT) at 0.5-second intervals.
Caution When the main system clock is operating at 5.0 MHz, it cannot be used to generate a 0.5-
second interval. In this case, the subsystem clock, which operates at 32.768 kHz, should
be used instead.
(2)
Interval timer
The interval timer is used to generate an interrupt request (INTWTI) at specified intervals.
Interval
× 1/f
4
2
W
× 1/f
5
2
W
× 1/f
6
2
W
× 1/f
7
2
W
× 1/f
8
2
W
× 1/f
9
2
W
Remarks 1. f
2. f
3. f
8.2 Watch Timer Configuration
The watch timer includes the following hardware.
Item
5 bits × 1
Counter
9 bits × 1
Prescaler
Control register
Watch timer mode control register (WTM)
172
CHAPTER 8 WATCH TIMER
Table 8-1. Interval Generated Using the Interval Timer
At f
= 5.0 MHz
X
409.6 µ s
819.2 µ s
1.64 ms
3.28 ms
6.55 ms
13.1 ms
: Watch timer clock frequency (f
W
: Main system clock oscillation frequency
X
: Subsystem clock oscillation frequency
XT
Table 8-2. Watch Timer Configuration
User's Manual U15075EJ1V0UM00
At f
= 4.19 MHz
At f
X
489 µ s
488 µ s
978 µ s
977 µ s
1.96 ms
1.95 ms
3.91 ms
3.91 ms
7.82 ms
7.81 ms
15.6 ms
15.6 ms
7
/2
or f
)
X
XT
Configuration
= 32.768 kHz
XT
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