Datasheet

Section 14 Watchdog Timer (WDT)
Rev. 4.00 Jun 06, 2006 page 384 of 1004
REJ09B0301-0400
14.4 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. When NMI interrupt request generation is selected in
watchdog timer mode, an overflow generates an NMI interrupt request.
14.5 Usage Notes
14.5.1 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 14.6 shows this operation.
Address
φ
Internal write signal
TCNT input clock
TCNT
NM
T
1
T
2
TCNT write cycle
Counter write data
Figure 14.6 Contention between TCNT Write and Increment