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17.4
Interrupts
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 WTCSR. OVF must
be cleared to 0 in the interrupt handling routine. When NMI interrupt request generation is
selected in watchdog timer mode, an overflow generates an NMI interrupt request.
17.5
Usage Notes
17.5.1
Contention between Watchdog Timer Counter (WTCNT) Write and Increment
If a timer counter clock pulse is generated during the T2 state of a WTCNT write cycle, the write
takes priority and the timer counter is not incremented. Figure 17.6 shows this operation.
Internal φ
Internal address
Internal write
signal
WTCNT input
clock
WTCNT
Figure 17.6 Contention between WTCNT Write and Increment
Rev. 1.0, 02/00, page 358 of 1141
WTCNT write cycle
T
T
1
2
N
M
Counter write data
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