Datasheet

Section 14 Watchdog Timer (WDT)
Rev. 3.00 Mar 21, 2006 page 354 of 788
REJ09B0300-0300
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 bit 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: Internal 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