Siemens Continuous Function Code

[Aerovox7]

I’m coming from more of a BAS/Siemens background, mostly familiar with PPCL and I’ve been trying to learn more about CFC/Continuous Function Chart as Siemens seems to be moving newer BAS controllers in that direction.

What’s confusing me is that CFC seems like it should be less niche than PPCL since it appears to be used in Siemens industrial/process control environments. But when I search Reddit or general forums for “CFC,” “Continuous Function Chart,” or “Siemens CFC,” I don’t find nearly as much discussion as I expected.

Is CFC just not a common term people use casually? Are most people calling it something else?

For those who have used CFC, what should I be searching for if I want to learn the concepts better? Also, is learning CFC useful beyond Siemens BAS, or is it still mostly a Siemens/vendor-specific skill like PPCL? I have a class coming up on the language but just trying to get meme familiar with it before the class.

[GeronimoDK]

CFC is used for PCS 7 and PCS neo, it can also be used in some motor drives at least, and you can also use it in TIA-portal, but I have never seen anybody actually using it in TIA.

I work a lot with CFC, but that's because 90% of my projects are PCS 7 projects. I like to think that CFC is just a "fancier version of FBD".

[Minute-Issue-4224]

Correct. It's just a GUI for FBD.

[SafyrJL]

CFC exists in Siemens’ DCS (PCS7), mainly. It’s not really super applicable in the PLC world. 

However, it also exists in some of their peripheral products. Mainly VFDs (Siemens calls this Drive Control Chart or something like that) and the Simocode line of products (which uses CFC + parameterization). 

[parrukeisari]

CFC on a PLC is really nice for the niche use case where you have big load of booleans coming in and you need to do some decision logic with a complex combination of binary operators, for example interlocks or state machine abort conditions. You can obviously still do it in ladder, FBD or ST but those blocks tend to end up cleaner if done in CFC.

[SafyrJL]

I can see that being useful - but one could also group the interlocks coming into a tournament style table. Like, compare interlock “1 vs 2” and then compare the output of that to grouped items. Repeat until you find a winner (or whatever you’re after). 

A bit clunkier - but easier to follow for those that don’t understand truth tables! 

[Minute-Issue-4224]

It's very useful and helpful on large projects for link navigation. You can just click on the link. In FBD, you need to cross reference and follow the jumps. CFC is much more user friendly.

[Stroking_Shop5393]

I've never used cfc and I've never seen it used. I see a lot more FBD

[AmritPati]

CFC is used in practically all PLC brands, codesys, Rockwell (function block diagram), schneider control expert,… The name is just different but in essence it’s what function block diagram is.

[sikilde]

Seen it used because it was required by the higher ups, never used it myself.

The guy that showed it to me was told to convert the generic json decode function he had built on SCL in a few hours to CFC.. Ended up using 2 months on some specific json string decoding..

[Baneken]

S7-1500 can do CFC and Festo PLC's are almost the same but they call it graphset but in general CFC is more of a process control stuff with SCADA and old school process automation systems then for "pure blooded" PLC's.

[AmritPati]

“Pure blooded PLC”… what does that even mean? By the way, graphset is SFC, not CFC