Datasheet

Table Of Contents
Section 16 Watchdog Timer
Rev. 2.00 Jul. 04, 2007 Page 343 of 692
REJ09B0309-0200
16.3.2 Interval Timer Mode
Figure 16.3 shows the operation in interval timer mode. To use the WDT as an interval timer, set
the WT/IT bit in TCSRWD2 to 1.
When the WDT is used as an interval timer, an interval timer interrupt request is generated each
time the TCWD overflows. Therefore, an interval timer interrupt can be generated at intervals.
TCWD
count value
H'00
Time
H'FF
WT/IT = 1
Interval timer
interrupt
request generated
Interval timer
interrupt
request generated
Interval timer
interrupt
request generated
Interval timer
interrupt
request generated
Interval timer
interrupt
request generated
Figure 16.3 Interval Timer Mode Operation
16.3.3 Timing of Overflow Flag (OVF) Setting
Figure 16.4 shows the timing of the OVF flag setting. The OVF flag in TCSRWD2 is set to 1 if
TCWD overflows. At the same time, a reset signal is output in watchdog timer mode and an
interval timer interrupt is generated in interval timer mode.
φ
TCWD
H'FF H'00
Overflow signal
OVF
Figure 16.4 Timing of OVF Flag Setting