4583 Datasheet, PDF (44/153 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4583 Group
PRELIMINARY
Notice: This is not a final specification.
Some parametric limits are subject to change.
When the watchdog timer is used, clear the WDF1 flag at the pe-
riod of 65534 machine cycles or less with the WRST instruction.
When the watchdog timer is not used, execute the DWDT instruc-
tion and the WRST instruction continuously (refer to Figure 33).
The watchdog timer is not stopped with only the DWDT instruction.
The contents of WDF1 flag and timer WDT are initialized at the
RAM back-up mode.
When using the watchdog timer and the RAM back-up mode, ini-
tialize the WDF1 flag with the WRST instruction just before the
microcomputer enters the RAM back-up state (refer to Figure 34).
The watchdog timer function is valid after system is returned from
the RAM back-up. When not using the watchdog timer function, ex-
ecute the DWDT instruction and the WRST instruction continuously
every system is returned from the RAM back-up, and stop the
watchdog timer function.
WRST
; WDF1 flag cleared
DI
DWDT
WRST
; Watchdog timer function enabled/disabled
; WEF and WDF1 flags cleared
Fig. 33 Program example to start/stop watchdog timer
WRST
; WDF1 flag cleared
NOP
DI
; Interrupt disabled
EPOF
; POF instruction enabled
POF
↓
Oscillation stop
Fig. 34 Program example to enter the mode when using the
watchdog timer
Rev.3.00 Aug 06, 2004 page 44 of 151
REJ03B0009-0300Z