Glossary · System coordination, integration and orchestration
Acknowledgment signal
Also known as: ACK signal, acknowledge bit
German: Quittierungssignal
In industrial automation, an acknowledgment signal is a signal or message by which a receiving system confirms that it has received a request, command or data item from a sending system. It closes one step of a handshake so the sender knows it may proceed.
- System integration
In one sentence
An acknowledgment signal confirms that a command or data item has arrived, so the sending controller knows it may take the next step.
Example
After the line controller writes a new recipe number, the filler PLC sets its RecipeAck bit, and only then does the line controller clear the request bit.
How it applies
- Engineering: Define for every request which signal acknowledges it, whether the acknowledgment means “received” or “accepted,” and what the sender does when no acknowledgment arrives within the agreed Timeout.
- Commissioning: Test the acknowledgment path with the real partner system, including lost, late and duplicated acknowledgments, not only the normal sequence.
- Documentation: List acknowledgment signals in the Interface specification with data type, address, direction and reset condition. Signal tables in manuals should use the same names as the PLC tags so service technicians can trace a stalled sequence.
Acknowledgment signal vs. completion signal
An acknowledgment only confirms that a request has been received or accepted. A Completion signal reports that the requested action has actually finished. Treating an acknowledgment as proof of completion is a common integration error: the next machine starts before the previous one is ready.