M16C62_M Datasheet, PDF (473/615 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

Watchdog Timer
Mitsubishi microcomputers
M16C / 62A Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
2.11.2 Operation of Watchdog Timer
The following is an operation of the watchdog timer. Figure 2.11.3 shows the operation timing, and Figure
2.11.4 shows the set-up procedure.
Operation (1) Writing to the watchdog timer start register initializes the watchdog timer to 7FFF16 and
causes it to start a down count.
(2) With a count in progress, writing to the watchdog timer start register again initializes the
watchdog timer to 7FFF16 and causes it to resume counting.
(3) Either executing the WAIT instruction or going to the stopped state causes the watchdog
timer to hold the count in progress and to stop counting. The watchdog timer resumes count-
ing after returning from the execution of the WAIT instruction or from the stopped state.
(4) If the watchdog timer underflows, it is initialized to 7FFF16 and continues counting. At this
time, a watchdog timer interrupt occurs.
7FFF16
(1) Start count
(3) In stopped state, or WAIT
instruction is executing, etc
(2) Write operation
(4) Generate
watchdog timer
interrupt
000016
Write signal to the “H”
watchdog timer
start register
“L”
Figure 2.11.3. Operation timing of watchdog timer
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