I've been an AB programmer for many years and now I have a S7 job to work on.

I read so many manuals and I still don't understand S7 completely.I am Gonna Shoot some questions and feel free to answer if you have time.

1. I know by now that OBs are optional and if we encounter a fault the PLC will stop if the block is not included in the project. However, What If I include the block and I want certain faults to keep stop the PLC and other faults to keep it running but display faults?? Is there a way to do that??

2. I still dont understand the whole generate system messeges thing.. Do you have information on it? What if I am not using a Siemens HMI and i wanna capture the faults and display them??

Thank you

 

Not to worry,

Even Siemens doesn't understand S7 completely.

Regards
cww

 

1) No problem, you can use SFC46 or SFB20 to stop the CPU

2) You don't need to work with messages system to get alarm visible. A simple alarm bit oriented approach works fine

 

I am looking at some (Plant Running ) S7 files . Some of them Have logic in OB82. My question is why would somebody added some protected logic to the system OBs??

Isn't OB82 sufficent to capture Profibus fault?? Any Idea what kind of logic would be added to OB82??

 

Normally you would program messaging / reactions or triggers depending on kind of fault detected.