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Rev. 1.00, 05/04, page 229 of 544
11.4.2 Interval Timer Mode
When the WDT is used as an interval timer, an interval timer interrupt (WOVI) is generated each
time the TCNT overflows, as shown in figure 11.3. Therefore, an interrupt can be generated at
intervals.
When the TCNT overflows in interval timer mode, an interval timer interrupt (WOVI) is requested
at the same time the OVF bit of TCSR is set to 1. The timing is shown figure 11.4.
TCNT value
H'00
Time
H'FF
WT/IT = 0
TME = 1
WOVI
Overflow Overflow Overflow Overflow
[Legend]
WOVI : Internal timer interrupt request occurrence
WOVI WOVI
WOVI
Figure 11.3 Interval Timer Mode Operation
φ
TCNT
H'FF H'00
Overflow signal
(internal signal)
OVF
Figure 11.4 OVF Flag Set Timing