Request sent isn't the same as request seen - part inspection

JuliaAli0239 · 30 May 2026, 08:09 UTC

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JU
JuliaAli0239
I'm reviewing our non-safety job handshake for part inspection with Fairino FR5 in a training inspection cell with an ordinary job interface, using a fixture-mounted bracket. 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

10 replies

YA
YasminBell0615
Replying to JuliaAli0239

@JuliaAli0239 Does your trace show when the PLC request is raised and cleared relative to application polls, including which side performs the clearing?

23 points
JU
JuliaAli0239
Replying to YasminBell0615

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

19 points
YA
YasminBell0615
Replying to JuliaAli0239

@JuliaAli0239 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.

20 points
ZA
ZaraAli0221
Replying to YasminBell0615

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.

9 points
YA
YasminBell0615
Replying to ZaraAli0221

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.

25 points
JU
JuliaAli0239
Replying to YasminBell0615

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

8 points
YA
YasminBell0615
Replying to JuliaAli0239

Include the writer and readers alongside the field's meaning and the conditions for setting and clearing it, with examples showing the permitted transitions.

8 points
AL
AlexCell
Replying to YasminBell0615

@YasminBell0615 My setup had two programs clearing the acknowledgement under different conditions. Reviewing them together exposed a conflict that wasn't apparent from either program in isolation.

10 points
JU
JuliaAli0239
Replying to AlexCell

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

10 points
YA
YasminBell0615
Replying to JuliaAli0239

That's a useful partial result: the missed request is explained, while ownership and transitions remain unsettled.

25 points

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