Glossary · Data, timing and communication
Timeout
Also known as: time-out
In systems engineering, a timeout is a defined time limit after which a missing response is treated as a fault or exception.
- Data and interfaces
- Functional safety
In one sentence
A timeout turns silence into a detectable fault: after a defined time without a response, the system stops waiting and reacts.
Example
A safety PLC in a robot cell expects a message from its remote safety I/O every 20 ms; if none arrives within the configured watchdog time, it switches the outputs off.
How it applies
- Integrated systems: Choose timeouts from the measured worst-case latency plus a margin. Too short causes spurious trips, too long delays fault detection. Document each timeout and what it triggers.
- Functional safety: Safety communication typically monitors message arrival with a watchdog time. The timeout counts toward the response time of the safety function, and its expiry must lead to a defined fault reaction.
- Human factors: Frequent timeouts caused by unrealistic values lead to nuisance trips, which in turn tempt people to bypass protective measures.
Timeout vs. retry
A timeout decides that an attempt has failed; a retry is the next attempt. The number of attempts, the timeout and the backoff together determine how long a failure can remain unhandled.