UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 404

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

CHAPTER 12 WATCHDOG TIMER FUNCTION
12.4.2 Cautions on PD784026 Subseries Watchdog Timer
(1) The watchdog timer mode register (WDM) can only be written to with a dedicated instruction (MOV WDM, #byte).
(2) The same value should be written each time in writes to the watchdog timer mode register (WDM) to set (1) the RUN
bit. The contents written the first time cannot be changed even if a different value is written.
(3) Once the RUN bit has been set (1), it cannot be reset (0) by software.
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