Datasheet

Section 13 Watchdog Timer (WDT)
Rev. 6.00 Mar. 18, 2010 Page 474 of 982
REJ09B0054-0600
TCNT value
H'00
Time
H'FF
WT/IT=1
TME=1
Write H'00'
to TCNT
WT/IT=1
TME=1
Write H'00'
to TCNT
518 system clock (WDT0)
515/516 system clock (WDT1)
Internal reset signal
*
WT/IT:
TME:
WOVF:
Note: * In the case of WDT_0, the internal reset signal is generated only when the RSTE bit is set to 1.
In the case of WDT_1,either the internal reset or the NMI interrupt is generated.
Overflow
internal reset is
generated
WOVF=1
Timer mode select bit
Timer enable bit
Overflow flag
Legend:
Figure 13.2 Watchdog Timer Mode Operation
13.4.2 Interval Timer Mode
To use the WDT as a watchdog timer, set the WT/IT and TME bits in TCSR to 1.
When the WDT is used as an interval timer, an interval timer interrupt (WOVI) is generated each
time the TCNT overflows. (The NMI interrupt is not generated.) Therefore, an interrupt can be
generated at intervals.