Datasheet

Section 14 Watchdog Timer (WDT)
Rev. 3.00 Sep. 28, 2009 Page 397 of 910
REJ09B0350-0300
14.4.2 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 14.3. 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 flag of TCSR is set to 1. The timing is shown figure 14.4.
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 14.3 Interval Timer Mode Operation
φ
TCNT
H'FF H'00
Overflow signal
(internal signal)
OVF
Figure 14.4 OVF Flag Set Timing