429
12.4 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 TCSR. OVF must be
cleared to 0 in the interrupt handling routine.
If an NMI request has been chosen in the watchdog timer mode, an NMI request is generated
when a TCNT overflow occurs.
12.5 Usage Notes
12.5.1 Contention between Timer Counter (TCNT) Write and Increment
If a timer counter clock pulse is generated during the T
2
state of a TCNT write cycle, the write
takes priority and the timer counter is not incremented. Figure 12-8 shows this operation.
Address
ø
Internal write signal
TCNT input clock
TCNT
NM
T
1


T
2


TCNT write cycle
Counter write data
Figure 12-8 Contention between TCNT Write and Increment
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