Datasheet

Section 14 Watchdog Timer (WDT)
Rev. 4.00 Sep 27, 2006 page 418 of 1130
REJ09B0327-0400
TCNT count
H'00
Time
H'FF
WT/IT = 0
TME = 1
WOVI
Overflow Overflow Overflow Overflow
Legend:
WOVI: Interval timer interrupt request generation
WOVI WOVI WOVI
Figure 14.4 Operation in Interval Timer Mode
14.3.3 Timing of Setting of Overflow Flag (OVF)
The OVF flag is set to 1 if TCNT overflows during interval timer operation. At the same time, an
interval timer interrupt (WOVI) is requested. This timing is shown in figure 14.5.
If NMI request generation is selected in watchdog timer mode, when TCNT overflows the OVF
bit in TCSR is set to 1 and at the same time an NMI interrupt is requested.
φ
TCNT H'FF H'00
Overflow signal
(internal signal)
OVF
Figure 14.5 Timing of OVF Setting