Pausing the execution of a PLC program

I did this back in 1997 by putting a loop around the code where I toggled a bit. Was able to learn a lot about the way AB would execute false to true type instructions. I.e. you could reset the EN bit and have the instruction execute every scan. learned that the LIFO you needed to reset the EU bit.
 
Right... Because nothing can go wrong with a hardwired circuit. No possibility of poor circuit design or component failure there -- especially if you've done a risk assessment and used the red colored components.

Sorry. Just feeling a little snarky this morning. ;)

If you have followed ISO/EN 13849-1 and ISO/EN 13849-2, then technically it won't.

Although using some cheap as f**k PLC to do your safety circuit, then my guess is the OP (who could be dead after all this time) couldn't use any ISO to fight his way out of a wet paper bag.
 
Do yourself a favor and do not count on the PLC to for Human safety. A million things could happen in the PLC from program an error to an output failing. Hard wire the access door (or whatever) to your safety circuit.

Jim

I work for a company that builds all kinds of control panels with PLC's, and we NEVER stop the execution of PLC as a safety means.

We will always design the panel to break the circuit through hardwire connections and this is for safety reasons.
 

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