Datasheet

Section 12 Watchdog Timer (WDT)
Rev. 2.00 Aug. 20, 2008 Page 424 of 1198
REJ09B0403-0200
12.4.2 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 12.3. 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 in figure 12.4.
TCNT value
H'00
Time
H'FF
WT/IT = 0
TME = 1
WOVI
Overflow Overflow Overflow Overflow
WOVI : Interval timer interrupt request occurrence
WOVI WOVI
WOVI
Figure 12.3 Interval Timer Mode Operation
φ
TCNT
H'FF H'00
Overflow signal
(internal signal)
OVF
Figure 12.4 OVF Flag Set Timing