Author: PLC Play Ground
PLC Resends a Command Every Scan? Separate State Entry From State Activity
An action intended once on entering a state can accidentally run throughout that state.
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Two PLC Transitions Turn True Together? Decide Which One Wins
A sequence needs a defined outcome when more than one transition is true.
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PLC Timeout Starts Before the Device Gets the Command? Move the Reference Point
A timeout is meaningful only when its starting event is defined.
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Pause, Stop, and Abort Share One Button Path? Review Recovery Behavior
Different interruption commands can require different recovery paths.
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PLC Runs a Fresh Batch With an Old Completion Flag? Add Transaction Identity
A completion bit left over from earlier work can incorrectly finish a new transaction.
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Machine Skips Several Steps in One Scan? Inspect State Assignment Order
A sequence may advance through several states during one task execution if later logic sees earlier state assignments immediately.
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PLC Parallel Branch Waits Forever? Define the Join Condition
Parallel actions need a precise rule for joining again.
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PLC Recovery Retries Forever? Put a Budget on Automatic Attempts
Automatic retries need a defined stopping condition.
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PLC Heartbeat Toggles but the Consumer Misses It? Use a Better Health Contract
A toggling heartbeat can appear unchanged if the consumer samples it at an unfortunate interval.
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PLC Function Block Reports CommandAborted? Do Not Treat It as Done
An interrupted motion command is not the same as a completed move.
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