Renesas Hitachi H8S/2191, Hardware Manual, Page: 429 / 1065

Rev. 2.0, 11/00, page 402 of 1037
18.4 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.
18.5 Usage Notes
18.5.1 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 18.6 shows this operation.
Internal address
Internal
Internal write
signal
WTCNT input
clock
WTCNT
N M
T
1
T
2
WTCNT write cycle
Counter write data
Figure 18.6 Contention between WTCNT Write and Increment