RSLogix5000 structural text correlation with PLC scan

[daba]

Might I ask how the ControlLogix updates though?

here's the flowchart from the manual - note that the automatic update at the end of each task only applies to local I/O. In that respect, it appears to serve little purpose.

 

[Ron Beaufort]

TIP: you can find that same flowchart in the COMPACT-Logix manual too - but with just the name changed from "CONTROL-Logix" to "COMPACT-Logix" ... personally, I think that's just a "Copy-Paste" error ...

specifically, I haven't found any COMPACT-Logix systems (so far) that allow their input modules to be set up with COS (Change Of State) ... with that in mind, I'm not sure how the published COMPACT-Logix flow chart could possibly be correct ...

I've got quite a bit of work to do before next Monday at 8:00 AM - but if I can come up with some spare time, I'll try to put together some experiments to demonstrate how this stuff really works "under-the-hood" ... NOTE: I "THINK" that there's going to be a breakpoint between some older versions of RSLogix and the newer versions of RSLogix where the COMPACT-Logix rules are going to change ... this is going to take some time and work - because you can't always trust the books ...

(and a special thanks to daba) ...

 

[janner_10]

Thanks for sharing your experience. I wasn't aware that structural text is a taboo of sorts.

It is not taboo as such just difficult for the standard maintenance guy to understand. Although on average how many actually need to be routing around inside your software is up for debate. It certainly seems to be a States & Rockwell thing. (Our UK customers don't seem to specify language or even manufacturer as much as our American customers)

You program (unless specifically asked by the customer / your own company policy) in whatever language you prefer using.

Bear in mind though, using ST in Rockwell compared to say Siemens or Codesys is a not an enlightening experience.

You can write and layout your program in pretty much the same way but when you go online the state of the variables is in a watch table at the bottom of the screen, which makes following your online code very difficult.

In my experience ladder in Rockwell is probably the industry benchmark, it is excellent. Sadly ST is miles behind that curve and they really need to catch up.

 

[Salman S.]

Thanks daba the flowchart really puts things into perspective.

Bear in mind though, using ST in Rockwell compared to say Siemens or Codesys is a not an enlightening experience.

Following structural text isn't much of an issue for me as it resembles most programming languages. However, it is not so pleasant to program within RSLogix and I might as well go the route that appeals to most Rockwell customer base (as you eloquently put it, industry benchmark).