Datasheet

Section 14 Watchdog Timer
Rev. 3.00 Mar 17, 2006 page 655 of 926
REJ09B0283-0300
TCNT count
H'00
Time
H'FF
WT/IT=1
TME=1
H'00 written
to TCNT
WT/IT=1
TME=1
H'00 written
to TCNT
132 states
*
2
518 states
WDTOVF signal
Internal reset signal
*
1
WT/IT
TME
Notes: 1. If TCNT overflows when the RSTE bit is set to 1, an internal reset signal is generated.
2. 130 states when the RSTE bit is cleared to 0.
Overflow
WDTOVF and
internal reset are
generated
WOVF=1
: Timer mode select bit
: Timer enable bit
Legend:
Figure 14.2 Operation in Watchdog Timer Mode
14.4.2 Interval Timer Mode
To use the WDT as an interval timer, set the WT/IT bit to 0 and TME bit 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. 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 in the TCSR is set to 1.