Motion Done Bit Arrived—Why Is the Axis Still Not Ready for the Next Step?
A motion instruction's done indication answers the question defined by that instruction. The next process step may require additional conditions such as position tolerance, settling, tooling state, or valid feedback. Read the status semantics instead of treating every done bit as a complete machine-ready signal.
Application-state distinction; individual motion instructions have different completion semantics.
What is happening?
Command acceptance, execution completion, axis status, and process completion are separate concepts. Different instructions expose different combinations of status bits and error information. Application logic needs a reviewed transition condition that reflects the process requirement without inventing undocumented motion semantics.
Check these five things
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Identify the exact instruction and read the meaning and reset behavior of its status outputs.
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Separate command acceptance from execution and from the process-ready condition.
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Check relevant axis state, feedback quality, and independently required tooling conditions.
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Test interrupted, aborted, superseded, and failed commands in simulation.
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Document which conditions allow the next sequence step and why.
Worked example
A positioning operation completes according to its library, but a separate fixture confirmation remains false. Advancing the process solely on the motion status skips a required condition. The missing fixture signal is an application issue, not necessarily a motion-command defect.
Quick diagnostic reference
| State | Question |
|---|---|
| Command accepted | Was the request valid? |
| Motion status | What did the instruction finish? |
| Process ready | Are all next-step conditions satisfied? |
The mistake to avoid
Do not add a guessed fixed delay to every move as a substitute for understanding status and feedback. Define the actual requirement.
How to verify the fix
Demonstrate correct sequence behavior for successful, failed, interrupted, and recovered moves using the documented status rules.
Field-work boundary: These are educational diagnostic guides. Use the exact equipment manuals and approved site procedures. Electrical testing and machinery changes belong to qualified, authorized personnel; control hazardous energy and validate affected functions before release.
Technical reference
Rockwell Automation: motion instruction status reference. The examples and diagnostic tables above are original teaching material; they do not replace the product manual.