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CHAPTER 9 WATCH TIMER FUNCTION
314
User’s Manual U15109EJ3V0UD
9.4.2 Operation as interval timer
The watch timer can also be used as an interval timer that repeatedly generates an interrupt at intervals specified
by a preset count value.
The interval time can be selected by bits 4 to 6 (WTNM4 to WTNM6) of the watch timer mode control register
(WTNM).
Table 9-3. Interval Time of Interval Timer
WTNM6
WTNM5
WTNM4
Interval Time
f
W
= 32.768 kHz
0
0
0
2
4
×
1/f
W
488
µ
s
0
0
1
2
5
×
1/f
W
977
µ
s
0
1
0
2
6
×
1/f
W
1.95 ms
0
1
1
2
7
×
1/f
W
3.91 ms
1
0
0
2
8
×
1/f
W
7.81 ms
1
0
1
2
9
×
1/f
W
15.6 ms
1
1
0
2
10
×
1/f
W
31.2 ms
1
1
1
2
11
×
1/f
W
62.4 ms
Remark
f
W
: Watch timer clock frequency
Figure 9-2. Operation Timing of Watch Timer/Interval Timer
Start
5-bit counter
Overflow
Overflow
0H
Interrupt time of watch timer (0.5 s)
Interrupt time of watch timer (0.5 s)
Interval time
(T)
Interval time
(T)
Count clock f
W
or
f
W
/2
9
Watch timer
interrupt INTWTN
Interval timer
interrupt INTWTNI
nT
nT
Remark
f
W
: Watch timer clock frequency
( ): f
W
= 32.768 kHz
n:
Number of interval timer operations