Hello everybody, 

I'm seeing for the first time the usage of FB 216 in an other project, in particular on secure gates. I have looked into the tool guide (pressing F1 on the function) but it didn't help me a lot, so I have not so clear the situation, I would like to see (PDF or other post , I have not found many, just 11) some concret example in order to understand much better than now. 

Sbartoc,

try this :

https://www.google.it/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiLwLzy-ZjMAhWCcRQKHR3qDhwQFggkMAA&url=https%3A%2F%2Fsupport.industry.siemens.com%2Fcs%2Fattachments%2F22099875%2FS7_distributed_safety_configuring_and_programming_en_US_en-US.pdf%3Fdownload%3Dtrue&usg=AFQjCNFknplvk05XfXgmne7tEbpIXMMAbg

First example.

FDO-LINE-PWR is the output to safety contactor, while DI-SAFETY-FEEDBACK is the feedback from safety contactor. Other blocks are:
-EStopZone_FB is the e-stop evaluation for doors, light barrier, safety key. It has to be reset (ack) each time - this block gives the safety signal to F-FDBACK to close the safety contactor.
-EstopMushrooms this evaluates only the red e-stop switches: mushrooms. When the mushrooms are retracted, the output goes on automaticly- doesn't need to be reset (ack) - this block gives the safety signal to EStopZone_FB and to the other machine (external).

Despite looking at countless examples, I cannot make the FDBACK instruction ever work (attain a True output).   Oh, well looks like we'll have to create our own timer and logic.

Why is it that the Siemens examples for this particular instruction are the most useless?