EIC 1131 Design - SFC Question

[SCADA_Dude]

I am trying to make use of a sequencial flow chart to esentially serve as my main() program. I really like this elegant approach, but I have a basic implementation question I'd like to ask the more experienced EIC programmers out there.

I have broken my process down into logical steps and defined the transitions. My question is, where to you place functions that must be constantly monitored such as pressure alarms, etc. For these routines, there is no transition - I always want to monitor them.

Is it ok to place them in a seperate program to be run in parallel to the main SFC or is this messy programming? (I kind of think so)

Do I need to find a place to put them in the main SFC? (say on a parallel branch that is always true)

FYI: I'm programming in Unity Pro XL 3, not that is should matter.

Thanks
Kurt

 

[Peter Nachtwey]

That is why there are 5 IEC languages.

Do the polled routines in IL, LD, FBD or ST in a separate task from the SFC.

If you must use SFC for polling I/O then break the loop into logical groups of items ( actions )that must be polled and poll them at intervals in a round robin fashion. This will require that a timer be used to trigger the transition. This way you can carefully control your can times. One can even put an action in the loop twice so that the high speed things are polled twice as often.

 

[Archie]

You could put them in an Action that is attached to every step in the SFC. This effectively makes it called all the time.

 

[SCADA_Dude]

Great ideas, I hadn't thought of those options. Thanks so much!

This forum is so helpful.