What is the primary role of a watchdog timer in a mission computer?

What is the primary role of a watchdog timer in a mission computer?

• A. It schedules tasks in a fixed-priority order.
• B. It monitors software liveness and resets or safe-states if not pinged.
• C. It manages memory protections for processes.
• D. It handles fault isolation by partitioning CPU cores.

Answer: (B)

The watchdog timer functions as a safety net that ensures the mission computer doesn’t stay stuck if software stops responding. The running software must periodically “ping” or refresh the watchdog. If that heartbeat doesn’t arrive within a preset timeout, the watchdog triggers a reset or moves the system into a safe-state to prevent unsafe or uncontrolled operation. This behavior is key for reliability in critical systems, providing automatic recovery from hangs or crashes. This role is different from scheduling tasks (which is handled by the scheduler), memory protection (handled by memory management/OS), or fault isolation by partitioning cores (which is about separating components for safety). The watchdog’s job is specifically to detect loss of software liveness and enforce a safe recovery.

The watchdog timer functions as a safety net that ensures the mission computer doesn’t stay stuck if software stops responding. The running software must periodically “ping” or refresh the watchdog. If that heartbeat doesn’t arrive within a preset timeout, the watchdog triggers a reset or moves the system into a safe-state to prevent unsafe or uncontrolled operation. This behavior is key for reliability in critical systems, providing automatic recovery from hangs or crashes.

This role is different from scheduling tasks (which is handled by the scheduler), memory protection (handled by memory management/OS), or fault isolation by partitioning cores (which is about separating components for safety). The watchdog’s job is specifically to detect loss of software liveness and enforce a safe recovery.