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CHAPTER 8 WATCH TIMER
User’s Manual U15075EJ2V1UD
181
Figure 8-3. Watch Timer/Interval Timer Operation Timing
0H
Start
Overflow
Overflow
5-bit counter
Count clock
f
W
/2
9
Watch timer
interrupt
INTWT
Interval timer
interrupt
INTWTI
Watch timer interrupt time (0.5 s)
Watch timer interrupt time (0.5 s)
Interval
timer (T)
T
Caution When operation of the watch timer and 5-bit counter operation is enabled by setting bit 0
(WTM0) of the watch mode timer mode control register (WTM) to 1, the interval until the first
interrupt request (INTWT) is generated after the register is set does not exactly match the watch
timer interrupt time (0.5 s). This is because there is a delay of one 9-bit prescaler output cycle
until the 5-bit counter starts counting. Subsequently, however, the INTWT signal is generated
at the specified intervals.
Remarks
1.
f
W
: Watch timer clock frequency
2.
The parenthesized values apply to operation at f
W
= 32.768 kHz.