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CHAPTER 8 WATCH TIMER
Preliminary User’s Manual U16035EJ1V0UM
(1) Watch timer
When the main system clock or subsystem clock is used, interrupt requests (INTWT) are generated at 2
14
/f
W
second intervals.
Remark
f
W
: Watch timer clock frequency (f
X
/2
7
or f
XT
)
f
X
: Main system clock oscillation frequency
f
XT
: Subsystem clock oscillation frequency
(2) Interval timer
Interrupt requests (INTWTI) are generated at the preset time interval.
Table 8-1. Interval Timer Interval Time
Interval Time
When Operated at
When Operated at
When Operated at
f
X
= 8.38 MHz
f
X
= 4.19 MHz
f
XT
= 32.768 kHz
2
11
×
1/f
X
2
4
×
1/f
XT
244
µ
s
489
µ
s
488
µ
s
2
12
×
1/f
X
2
5
×
1/f
XT
489
µ
s
978
µ
s
977
µ
s
2
13
×
1/f
X
2
6
×
1/f
XT
978
µ
s
1.96 ms
1.95 ms
2
14
×
1/f
X
2
7
×
1/f
XT
1.96 ms
3.91 ms
3.91 ms
2
15
×
1/f
X
2
8
×
1/f
XT
3.91 ms
7.82 ms
7.81 ms
2
16
×
1/f
X
2
9
×
1/f
XT
7.82 ms
15.6 ms
15.6 ms
Remark
f
X
: Main system clock oscillation frequency
f
XT
: Subsystem clock oscillation frequency
8.2 Configuration of Watch Timer
The watch timer consists of the following hardware.
Table 8-2. Configuration of Watch Timer
Item
Configuration
Counter
5 bits
×
1
Prescaler
9 bits
×
1
Control register
Watch timer operation mode register (WTM)