Reviewing a missed request without confusing it with rejection - fixture inspection

ClaraAli0176 · 25 Jul 2026, 06:24 UTC

Reply to discussion
CL
ClaraAli0176
Our application sometimes misses the PLC's brief request for fixture inspection. I'm reviewing that ordinary, non-safety handshake for Fairino FR10 in a training inspection cell with an ordinary job interface, with a reference plate in the setup. Signal ownership and clearing conditions aren't clearly documented. The safety functions are independently engineered and separate from this job interface.

11 replies

NO
NoahChen1151
Replying to ClaraAli0176

Can you compare the request trace with your application's polls? Also note which side clears the request.

8 points
CL
ClaraAli0176
Replying to NoahChen1151

Our trace shows it rising and falling between two polls. The PLC clears it without an observed acknowledgement. No wonder the application misses it.

22 points
NO
NoahChen1151
Replying to ClaraAli0176

@ClaraAli0176 Draft one writer and clear conditions for each field, then review a request retained until matching acknowledgement with the interface owner. That should settle the handshake offline.

9 points
HE
HenryBrooks0786
Replying to NoahChen1151

Settle it? Retaining a request fixes visibility, but can also keep an old request alive after a restart. Identity and reset rules matter.

15 points
NO
NoahChen1151
Replying to HenryBrooks0786

@HenryBrooks0786 Yes, I overstated that. Retention addresses the missed pulse. The offline review also needs matching identity, reset ownership and restart cases before the design is complete.

13 points
CL
ClaraAli0176
Replying to NoahChen1151

Would your table include who reads each field too? Our notes say used by PLC, which could mean practically anything.

4 points
NO
NoahChen1151
Replying to ClaraAli0176

@ClaraAli0176 Yes: writer, readers, meaning, set condition and clear condition. Then give each legal transition a concrete example.

17 points
PR
PriyaBarnes0568
Replying to NoahChen1151

On my interface, both sides cleared acknowledgement for different reasons. Each program looked reasonable alone. Put them together and the answer vanished

6 points
CL
ClaraAli0176
Replying to PriyaBarnes0568

@PriyaBarnes0568 I've checked our assignments and found that too: both sides can clear acknowledgement. I'll put both conditions in the review rather than quietly choose one.

21 points
CL
ClaraAli0176
Replying to ClaraAli0176

The missed pulse is explained, and I've got an ownership review to work from. Our complete handshake behaviour is still open.

20 points
NO
NoahChen1151
Replying to ClaraAli0176

@ClaraAli0176 The trace gives the review a concrete starting point. Keeping the overall handshake open is fair.

13 points

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