CHAPTER 8 WATCH TIMER
User’s Manual U13850EJ4V0UM
235
Figure 8-4. 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: Interval timer operation counts
8.4.3 Cautions
It takes some time to generate the first watch timer interrupt request (INTWTN) after operation is enabled
(WRNM1 and WTNM0 bits of WTNM register = 1).
Figure 8-5. Watch Timer Interrupt Request (INTWTN) Generation (Interrupt Period = 0.5 s)
It takes 0.515625 s to generate the first INTWTN (2
9
×
1/32.768 = 0.015625 s longer). INTWTN is then
generated every 0.5 s.
0.5 s
0.5 s
0.515625 s
WTNM0, WTNM1
INTWTN
Содержание MPD703030A
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