HD64F3337YCP16V Datasheet, PDF (264/749 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

11.4.4 Switching between Watchdog Timer Mode and Interval Timer Mode
If a switch is made between watchdog timer mode and interval timer mode while the WDT is
operating, correct operation may not be performed. The WDT must be stopped (by clearing the
TME bit to 0) before changing the timer mode.
11.4.5 Detection of Program Runaway
The following points should be noted when using the microcomputer’s on-chip watchdog timer to
detect program runaway.
During program runaway, instructions other than the usual instructions may be executed. If an
instruction reserved for system use is executed as a result of runaway, the watchdog timer may
sometimes stop, preventing detection of the runaway.
This problem can be avoided by making the following settings in the program.
1. Set code H'0004 in ROM address H'0002.
2. Set code H'56F0 in ROM address H'0004.
As system reserved addresses may be used by an emulator, the above settings should only be made
for the real chip.
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