UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 338

• Manufacturer Part Number: UPD78F0838
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

9.1 Functions of Watchdog Timer
signal is generated.
For details of RESF, see CHAPTER 21 RESET FUNCTION.
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The watchdog timer operates on the internal low-speed oscillation clock.
The watchdog timer is used to detect an inadvertent program loop. If a program loop is detected, an internal reset
Program loop is detected in the following cases.
When a reset occurs due to the watchdog timer, bit 4 (WDTRF) of the reset control flag register (RESF) is set to 1.
If the watchdog timer counter overflows
If a 1-bit manipulation instruction is executed on the watchdog timer enable register (WDTE)
If data other than “ACH” is written to WDTE
If data is written to WDTE during a window close period
If the instruction is fetched from an area not set by the IMS and IXS registers (detection of an invalid check while
the CPU hangs up)
If the CPU accesses an area that is not set by the IMS and IXS registers (excluding FB00H to FFCFH and
FFE0H to FFFFH) by executing a read/write instruction (detection of an abnormal access during a CPU program
loop)
CHAPTER 9 WATCHDOG TIMER
Preliminary User’s Manual U19748EJ1V0UD