SCADAPack 474 - Are program units supported and their uses

[Syrio]

I am just starting to learn RemoteConnect and I am wondering if Program Units are supported with the SCADAPack 474 RTU's. When I read the documentation it says they are only supported in M340/580 Processors. I am just wondering if the documentation has not been updated. 

I was also curious how people would typically use a Program Unit/Subroutine? I have worked primarily with Allen-Bradley Control Logix and Telepace Studio. It seems like there are many similarities to Control Logix. In the Mill I used to work at we would create an Individual Program for each machine such as a conveyor, cutting device, chipper, etc. and this worked very well. It made it very nice to be able to use the same tag names such as Start, Stop, Overload, etc. within an individual program and then call them from other programs if necessary by using the ProgramName.Start for example.

Does anyone have any sample programs with more advanced programming techniques? I am working on building a template program for our Lift Stations and Pump Station sites. 

Thanks

[BevanWeiss · Accepted solution]

Program Units are supported under the SCADAPack x70 devices.  However they are NOT supported with Quantum / Premium PLCs (hence the comment about them being supported on M340/M580.. Control Expert still has quite a bit of legacy stuff floating around in the documentation and other locations).

Given how convenient DFBs are to use in the Control Expert world, I've never really seen Program Units utilised.

I can imagine if there are several separate almost identical production lines within a single controller then it might make sense, but there are other ways to structure programs (using the Functional View) which tend to be a bit simpler.

There's also not much of a restriction on the length of variable names, so there's limited benefit to using Program Units to allow for separation of variable names.

I suspect that the Program Units would complicate things like searching for generic controls (like the Start/Stop etc that you mentioned).  So I'd generally prefer to handle these with tag name prefixes, with variables stored in the controller variable scoping.

Even in the Rockwell Studio5000 type of world, forcing the conceptualisation into Program scoping can be a real stitch-up at times.  From memory, a Program can only exist in a single Task.  So if you need to do things like Periodic Tasks / Event Tasks etc and interact with the Continuous Task then you start to have split Program scopes, which breaks flow between the tasks if you rely upon the Program scope for the variables.  If you use a tag prefix and controller scoped tags, then there is a straight forward flow between the data in the tasks.  Strongly defined program interfaces would help, but again from memory there are significant limitations to these around Online Edits.  And almost all of the Logix5000 applications I've dealt with have simply not allowed for Stop/Download type of code changes.  Most of the plants run 24/7 with minimal disruption to that schedule (monthly P.M. shuts.. or sometimes only an annual shutdown).

I'm unsure what limitations Control Expert might have on online changes around the Program Units (I suspect it would be 'better' than Rockwell... but there may still be significant limitations)