Remembered data and observed hardware state are different evidence.
Name what is retained
Siemens describes retentive data as selected memory information preserved across the stated power-loss condition. That defines data retention, not every external device's position. Primary reference: Siemens retentive-data scope.
Identify the stored command, the actual output behavior and any independently observed valve condition as separate fields. Their relationship needs the selected hardware and control design. A retained bit should not silently be presented as a newly observed position after restart.
A hypothetical restart record
Imagine a controller stores last requested state A before power disappears. After restart, an export restores that retained value but gives no fresh physical observation. The value documents the remembered request under its stated retention basis; it does not by itself confirm the external valve's current state.
Prepare columns for last command, retained-memory validity, output configuration, supply conditions and physical-state evidence where applicable. Keep unavailable evidence visible. The example concerns information interpretation, not an HM restart finding or instruction to energize a valve.
Preserve the actual recovery relationship
Ask the responsible designer how the real control sequence treats retained requests and current hardware conditions. Power and pneumatic-supply events can have their own relevant behavior; a generic memory feature cannot replace that defined system relationship.
Retain the selected controller configuration and valve function with the accepted restart record. If either changes, review the mapping instead of copying a remembered state as proof of recovery. This guide distinguishes software history from present hardware evidence without programming a recovery sequence or assuming every valve position is measured in the installed machinery.
Customer Questions
Does a retained command prove current valve position?
No. Identify the actual physical-state evidence.
Are memory validity and output behavior the same field?
No. Preserve their separate meanings.
Does this article supply a restart program?
No. It defines the information boundary.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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