Operation In Interval Timer Mode; Timing Of Overflow Flag (Ovf) Setting - Hitachi H8S/2338 Series Hardware Manual

10.3.2

Operation in Interval Timer Mode

To use the WDT as an interval timer, clear the WT/IT bit in TCSR to 0 and set the TME bit to 1.
An interval timer interrupt (WOVI) is generated each time TCNT overflows, provided that the
WDT is operating as an interval timer, as shown in figure 10-5. This function can be used to
generate interrupt requests at regular intervals.
TCNT count
H'FF
H'00
WT/IT=0
TME=1
Legend
WOVI: Interval timer interrupt request generation
10.3.3

Timing of Overflow Flag (OVF) Setting

The OVF flag is set to 1 if TCNT overflows during interval timer operation. At the same time, an
interval timer interrupt (WOVI) is requested. This timing is shown in figure 10-6.
ø
TCNT
Overflow signal
(internal signal)
OVF
Overflow
WOVI
Figure 10-5 Operation in Interval Timer Mode
H'FF
Figure 10-6 Timing of OVF Setting
Overflow Overflow
WOVI WOVI
Overflow
Time
WOVI
H'00
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