M30620FCAFP datasheet(473/615 Pages) RENESAS

473 / 615 page

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Watchdog Timer

2-156

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.

(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.

Operation

Figure 2.11.3. Operation timing of watchdog timer

(1) Start count

Write signal to the

watchdog timer

start register

7FFF16

000016

“H”

“L”

(4) Generate

watchdog timer

interrupt

(2) Write operation

(3) In stopped state, or WAIT

instruction is executing, etc

M30620FCAFP Datasheet(PDF) 473 Page - Renesas Technology Corp