M16C User Manual.pdf

Watchdog TimerMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER2.11.2 Operation of Watchdog TimerThe following is an operation of the watchdog timer. Figure 2.11.3 shows the operation timing, and Figure2.11.4 shows the set-up procedure.Operation(1) Writing to the watchdog timer start register initializes the watchdog timer to 7FFF16 andcauses it to start a down count.(2) With a count in progress, writing to the watchdog timer start register again initializes thewatchdog timer to 7FFF16 and causes it to resume counting.(3) Either executing the WAIT instruction or going to the stopped state causes the watchdogtimer to hold the count in progress and to stop counting. The watchdog timer resumes countingafter 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 thistime, a watchdog timer interrupt occurs.(1) Start count(3) In stopped state, or WAITinstruction is executing, etc(2) Write operation(4) Generatewatchdog timerinterrupt7FFF16000016Write signal to thewatchdog timerstart register“H”“L”Figure 2.11.3. Operation timing of watchdog timer428