205
CHAPTER 9 WATCH TIMER
User’s Manual U15798EJ2V0UD
(1) Watch timer
By using the main system clock or subsystem clock, interrupt requests (INTWTN0) are generated at preset
intervals.
An interrupt request (INTWTN0) occurs at an interval of 0.5 second when using the 32.768 kHz subsystem clock.
Also, an interrupt request (INTWTN0) can be generated at an interval of 1.0 seconds when using the 32.768 kHz
subsystem clock via a setting in the watch timer interrupt time select register (WTIM).
Table 9-1. Watch Timer Interrupt Request Time
Interrupt Request Time
When Operated at f
X
=
When Operated at f
XT
=
When Operated at f
XT
/2 =
10 MHz
32.768 kHz
16.384 kHz
2
4
/f
W
409.6
µ
s
488
µ
s
977
µ
s
2
5
/f
W
819.2
µ
s
977
µ
s
1.95 ms
2
13
/f
W
0.2 s
0.25 s
0.5 s
2
14
/f
W
0.41 s
0.5 s
1.0 s
Remark
f
W
: Watch timer clock frequency (f
X
/2
8
, f
XT
, or f
XT
/2)
f
X
:
Main system clock oscillation frequency
f
XT
: Subsystem clock oscillation frequency
(2) Interval timer
By using the main system clock or subsystem clock, interrupt requests (INTWTNI0) are generated at preset
intervals.
Table 9-2. Interval Timer Interval Time
Interval Time
When Operated at f
X
=
When Operated at f
XT
=
When Operated at f
XT
/2 =
10 MHz
32.768 kHz
16.384 kHz
2
4
/f
W
409.6
µ
s
488
µ
s
977
µ
s
2
5
/f
W
819.2
µ
s
977
µ
s
1.95 ms
2
6
/f
W
1.64 ms
1.95 ms
3.91 ms
2
7
/f
W
3.28 ms
3.91 ms
7.81 ms
2
8
/f
W
6.56 ms
7.81 ms
15.6 ms
2
9
/f
W
13.1 ms
15.6 ms
31.2 ms
2
10
/f
W
26.2 ms
31.2 ms
62.4 ms
2
11
/f
W
52.4 ms
62.4 ms
125 ms
Remark
f
W
: Watch timer clock frequency (f
X
/2
8
, f
XT
, or f
XT
/2)
f
X
:
Main system clock oscillation frequency
f
XT
: Subsystem clock oscillation frequency
Содержание mPD780344 Series
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