Interval Timer Operation; Timing Of Setting Overflow Flag (Ovf) - Renesas H8S Series Hardware Manual

13.3.2

Interval Timer Operation

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 13-5. This function can be used to generate interrupt requests at regular intervals.
TCNT count
H'FF
H'00
Legend:
WOVI: Interval timer interrupt request generation
13.3.3

Timing of Setting Overflow Flag (OVF)

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 13-6.
ø
TCNT
Overflow signal
(internal signal)
OVF
Overflow
WOVI
WT/IT=0
TME=1
Figure 13-5 Interval Timer Operation
H'FF
Figure 13-6 Timing of Setting of OVF
Overflow Overflow
WOVI WOVI
Overflow
Time
WOVI
H'00
Rev.6.00 Oct.28.2004 page 461 of 1016
REJ09B0138-0600H