Watchdog Timer Operation; Interval Timer Operation - Hitachi H8/3022 Hardware Manual

H'FF
TCNT count
value
H'00
Internal
reset signal
RESO
Figure 10-4 Watchdog Timer Operation (Masked ROM Version)

10.3.2 Interval Timer Operation

Figure 10-5 illustrates interval timer operation. To use the WDT as an interval timer, clear bit
WT/IT to 0 and set bit TME to 1 in TCSR. An interval timer interrupt request is generated at each
TCNT overflow. This function can be used to generate interval timer interrupts at regular
intervals.
H'FF
TCNT
count value
H'00
IT
WT/ = 0
TME = 1
318
Start H'00 written
in TCNT
Interval Interval
timer timer
interrupt interrupt
Figure 10-5 Interval Timer Operation
WDT overflow
TME set to 1
OVF = 1
Reset
518 states
132 states
Interval Interval
timer timer
interrupt interrupt
H'00 written
in TCNT
Time t
Interval
timer
interrupt