Datasheet

Section 13 Watchdog Timer
Rev.6.00 Mar. 18, 2009 Page 535 of 980
REJ09B0050-0600
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 13.2 Operation in Watchdog Timer Mode
13.4.2 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.