Under what circumstances will wdt fail

[zero]

Dear devzone，

Use our chip wdt module to feed the dog regularly. Under normal circumstances, if it is stuck in a dead loop, wdt does not feed the dog, and the wdt timeout chip will restart; under what circumstances will wdt fail? Customers need to know various wdt failure situations

BR，

Zero

[rajeev]

Here are the key scenarios where a watchdog timer may not work as intended:

1. Watchdog Not Properly Configured

• Disabled or Not Initialized: If the watchdog timer is not enabled in firmware/software, it won’t trigger a reset.

• Incorrect Timeout Setting: If the timeout is too long, the system may hang indefinitely before the watchdog resets it.

• Improper Feeding Mechanism: If the "kick" or "feed" signal is incorrectly implemented, the watchdog may reset the system unnecessarily or fail to detect a hang.

2. Software or Firmware Bugs Preventing Reset

• Infinite Loop with Watchdog Feed: If the system is stuck in a loop that still feeds the watchdog, it won’t trigger a reset.

• High-Priority Interrupts Blocking Execution: If an ISR (Interrupt Service Routine) keeps feeding the watchdog while the main application is frozen, the watchdog won’t fire.

• Race Conditions or Deadlocks: Some hangs may prevent the watchdog from being serviced but also avoid a timeout due to unexpected timing issues.

3. Hardware Failures

• Faulty Watchdog Circuit: If the watchdog hardware itself is defective, it may not issue a reset.

• Power Supply Issues: If voltage drops too low, the watchdog may not function correctly.

• Clock Signal Failure: If the system clock (which drives the watchdog) fails, the timer may stop counting.

4. External Interference

• EMI (Electromagnetic Interference): Strong noise can disrupt the watchdog’s operation.

• Radiation or Cosmic Rays (in space applications): Can cause bit flips in registers controlling the watchdog.

5. Watchdog Being Overridden

• Manual Reset Disables Watchdog: Some systems allow a debugger or external command to disable the watchdog.

• Brownout Reset Takes Priority: If the system resets due to power loss before the watchdog triggers, the watchdog may not act.

6. System-Specific Issues

• Multi-Core Systems: If one core hangs but others keep feeding the watchdog, the system may not reset.

• RTOS Task Scheduling Issues: A high-priority task might keep running and feeding the watchdog while lower-priority tasks are deadlocked.