Section 11 Watchdog Timer (WDT)
Rev. 3.00 Mar. 14, 2006 Page 373 of 804
REJ09B0104-0300
11.3.2
Interval Timer Mode
To use the WDT as an interval timer, set the WT/
IT
bit to 0 and the TME bit to 1 in TCSR.
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.
TCNT value
H'00
Time
H'FF
WT/
IT
= 0
TME = 1
WOVI
Overflow
Overflow
Overflow
Overflow
WOVI: Interval timer interrupt request
WOVI
WOVI
WOVI
Figure 11.3 Operation in Interval Timer Mode
11.4 Interrupt
Source
During interval timer mode operation, an overflow generates an interval timer interrupt (WOVI).
The interval timer interrupt is requested whenever the OVF flag is set to 1 in TCSR. The OVF flag
must be cleared to 0 in the interrupt handling routine.
Table 11.1 WDT Interrupt Source
Name Interrupt
Source
Interrupt Flag
DMAC Activation
WOVI TCNT
overflow
OVF
Impossible
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