Our application keeps missing a brief PLC request - fixture inspection

ZaraArcher0395 · 24 Jul 2026, 14:56 UTC

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ZA
ZaraArcher0395
I'm reviewing our non-safety job handshake for fixture inspection with Fairino FR10 in a training inspection cell with an ordinary job interface, using a sample housing. The PLC sends a brief request, and our application sometimes misses it. I can't find anything clear about who owns each signal or when it gets cleared. Safety functions are independently engineered; this is the ordinary job interface.

11 replies

NA
NaomiAllen0332
Replying to ZaraArcher0395

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

11 points
ZA
ZaraArcher0395
Replying to NaomiAllen0332

@NaomiAllen0332 I've compared the trace: the PLC raises and clears the request between consecutive application polls, with no observed acknowledgement before it clears.

9 points
NA
NaomiAllen0332
Replying to ZaraArcher0395

@ZaraArcher0395 Take an ownership table and a retained-request proposal to the interface owner. A request held until matching acknowledgement should settle the handshake in an offline review.

24 points
NA
NaomiBrown0941
Replying to NaomiAllen0332

Holding the request addresses the missed pulse, but it doesn't settle the interface. A retained request needs identity and restart rules to avoid being mistaken for new work.

1 points
NA
NaomiAllen0332
Replying to NaomiBrown0941

@NaomiBrown0941 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.

11 points
ZA
ZaraArcher0395
Replying to NaomiAllen0332

Should I record readers as well as the single writer? Our existing phrase used by PLC doesn't distinguish setting, reading or clearing a field.

21 points
NA
NaomiAllen0332
Replying to ZaraArcher0395

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

23 points
NA
NathanChen1156
Replying to NaomiAllen0332

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

18 points
ZA
ZaraArcher0395
Replying to NathanChen1156

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.

9 points
ZA
ZaraArcher0395
Replying to ZaraArcher0395

I can account for the unobserved request, but the interface ownership and wider transition behaviour still need resolving.

21 points
NA
NaomiAllen0332
Replying to ZaraArcher0395

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

8 points

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