Watchdog: Difference between revisions
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A [https://en.wikipedia.org/wiki/Watchdog_timer watchdog timer] is a feature of many high-reliability [[Real_Time|real-time]] systems. It takes the place of the (depressingly familiar) “try switching it off and on again” approach in far too many interactive, computerised goods. | A [https://en.wikipedia.org/wiki/Watchdog_timer watchdog timer] is a feature of many high-reliability [[Real_Time|real-time]] systems. It takes the place of the (depressingly familiar) “try switching it off and on again” approach in far too many interactive, computerised goods. | ||
A watchdog relies on an automated | A watchdog relies on an automated [https://en.wikipedia.org/wiki/Fail_safe fail-safe] process; it only comes into effect when something <em>doesn’t</em> happen. A successfully running system is expected to tell some supervisory layer – and eventually the real-time operating system – that it is still okay. If it fails to do this within a certain time it is assumed to have gone wrong and the hardware forces a [[reset]]. | ||
[https://en.wikipedia.org/wiki/Fail_safe fail-safe] process; it only | |||
comes into effect when something <em>doesn’t</em> happen. A successfully | |||
running system is expected to tell some supervisory layer – and | |||
eventually the real-time operating system – that it is still okay. | |||
If it fails to do this within a certain time it is assumed to have | |||
gone wrong and the hardware forces a [[reset]]. | |||
Here’s a little [http://www.ganssle.com/watchdogs.htm anecdote]. | Here’s a little [http://www.ganssle.com/watchdogs.htm anecdote]. | ||
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Latest revision as of 10:03, 5 August 2019
| Depends on | Real Time • Reset |
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A watchdog timer is a feature of many high-reliability real-time systems. It takes the place of the (depressingly familiar) “try switching it off and on again” approach in far too many interactive, computerised goods.
A watchdog relies on an automated fail-safe process; it only comes into effect when something doesn’t happen. A successfully running system is expected to tell some supervisory layer – and eventually the real-time operating system – that it is still okay. If it fails to do this within a certain time it is assumed to have gone wrong and the hardware forces a reset.
Here’s a little anecdote.
