Field Guide · concept

Also known as: watchdog, WDT

A watchdog timer (WDT) is a hardware counter that resets a system if the software fails to signal it within a set interval.1

Kick it in time, or it resets you full 0 count left kickkickkick hang — kicks stop hardware reset healthy code pets the dog before zero; a crashed one never does — so it reboots
The watchdog counts down continuously, and healthy firmware must "kick" it back to full before it reaches zero. Each kick resets the count; but if the code hangs or crashes the kicks stop, the counter runs out, and the watchdog forces a hardware reset — recovering an unattended device with no human present.

Overview

The watchdog counts down continuously; healthy firmware must periodically “kick” (reset) it before it reaches zero. If the code hangs in an infinite loop, deadlocks, or crashes, it stops kicking, the counter expires, and the watchdog forces a hardware reset — bringing the device back to a known state with no human intervention. Most microcontrollers include one as a dedicated peripheral, often clocked independently so it survives even if the main clock fails.

Where it fits

A watchdog is a core reliability tool for any unattended embedded system: an industrial controller, a remote sensor node, or a bootloader guarding a firmware update. The trick is kicking it only when the system is genuinely making progress — kicking it blindly from an interrupt defeats the purpose. It is the safety net under both bare-metal and RTOS-based designs.

Sources

  1. Watchdog timer — Wikipedia, on watchdog timers and recovery. ↩

See also

Learn it step by step