4524 datasheet(59/310 Pages) RENESAS

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FUNCTION BLOCK OPERATIONS

4524 Group

HARDWARE

Rev.2.00

Aug, 06 2004

REJ09B0107-0200Z

1-46

Fig. 31 Program example to start/stop watchdog timer

Fig. 32 Program example to enter the mode when using the

watchdog timer

WRST

; WDF1 flag cleared

NOP

; Interrupt disabled

EPOF

; POF instruction enabled

POF

↓

Oscillation stop

When the watchdog timer is used, clear the WDF1 flag at a cycle of

less than 65534 machine cycles with the WRST instruction.

When the watchdog timer is not used, execute the DWDT instruc-

tion and the WRST instruction continuously (refer to Figure 31).

The watchdog timer is not stopped with only the DWDT instruction.

The contents of WDF1 flag and timer WDT are initialized at the

power down mode.

When using the watchdog timer and the power down mode, initial-

ize the WDF1 flag with the WRST instruction just before the system

enters the power down state (refer to Figure 32).

The watchdog timer function is valid after system is returned from

the power down. When not using the watchdog timer function, stop

the watchdog timer function with the DWDT instruction and the

WRST instruction continuously every system is returned from the

power down.

WRST

; WDF1 flag cleared

DWDT

; Watchdog timer function enabled/disabled

WRST

; WEF and WDF1 flags cleared

4524 Datasheet(PDF) 59 Page - Renesas Technology Corp