Creating a Non-Scanning Routine in RSL5000

[JeffKiper 9]

We have a SI install a system with veeeery little documentation in the SFC. Steps, Tran. nothing has a description. We did not have a standard in place at that time. The boss told me to create a troubleshooting tool for the SFC and ST. I am thinking about a Routine that does NOT scan. Just to show the Steps in a ladder logic format. Making it easier to read for the guys that just don't get the Structured Text. Does anybody have a better idea? We are working in the training end of things. In the interim we need some help? As always thanks for you support and help!

[kaiser_will 65]

I would suggest creating a flowchart, on paper, of how the program works. Next, create a state machine in ladder logic that coincides with the flowchart. SFC's are terribly difficult, I have found, for maintenance guys to troubleshoot. If the machine has a lot of maintenance problems, eventually the electricians will want a new screen with state machine status lights (also known as the christmas tree). I always try to use the rule of thumb that all information should be binary...if you look at the status (state machine bits or state machine lights), is it very clear if things are working properly or not (yes or no...very binary). When you can drill diagnostics down to the binary level, your work on this project is done. Use this situation as an example for developing control system standards from vendors. Just wait until your boss buy a machine that has the password set. If it was a SLC, you can bypass the password and get online. If it is a ControlLogix CPU, good luck.

[Guest]

I’m not 100% sure what you’re asking for, Jeff ... but maybe this will help ... I’ve had excellent success in getting the basic ideas of SFCs across for beginning students by using this technique ... create a SFC (Sequential Function Chart) with about three steps ... put the ladder logic code for a “flashing lamp” in each step (timer, comparison, etc.) ... make sure each step uses a different timer and a different lamp ... choose the “lamp’s” address (actually an LED on an output module) 1-2-3 to match the FIRST, SECOND, or THIRD step of the SFC ... now set up the transitions to use simulator switches ... use a different switch 1-2-3 to match the number of the transition ... now step through the chart and watch the LEDs flash - depending of course on what specific step of the chart is active ... flip the appropriate switch to proceed from one step to the next ... develop a dog-and-pony show along the following lines ... “now the machine is loading” ... “now the press is active” ... “now the machine is unloading” ... note: if an LED occasionally “stays on” after you’ve left its step, then experiment with the setting on the “SFC Execution” tab of the “Controller Properties” feature ... is this sort of what you had in mind - or did I simply misinterpret your question? ...

[JeffKiper 9]

Yes and no Ron I should have explained myself better. I am in the process of documenting the program so that anybody can troubleshoot it. the Boss want it to see a ladder logic file "Not that Structured Text BS" I offered to him that we could recreate the program in a ladder version and download it debugging it and run doing away with the Sequential Function Blocks (SFC) and Structured Text (ST) totally. He did not like that idea he wanted to have a paper or some other form of documentation to reference. That is where my idea of a Routine that did not scan or do anything came into play. You would not have to keep up with a paper copy, no opening 2 or 3 projects just to troubleshoot 1. I thought if I could create this ladder in a file that did nothing more than set there it would become an indicator and maybe the boss would realize that it is OK to replace the SFC or ST. So my question is this possible in a CompactLogix? I would think so just by NOT using a JSR to that Routine but I am a newbie in the 5000 world. I hope this helps explain what and why I thought about doing.

[Gerry 13]

You should be insisting that the SI provide documentation. If you're having to trouble-shoot a newly installed system, then ahouldn't you have the SI involved to eliminate any bugs or at least to help train your people in how the system works? SFC's can be very useful for programming and subsequently fault-finding in a sequential operation. However, they are not necessarily appropriate for every application. It's not necessary to put all of the logic into the SFC using ST. Transitions only need to be a bit which can be set by ladder elsewhere. Actions can be ladder called by a JSR from the chart or simply conditioned by a "step active" status bit (<stepname>.x).

[Guest]

I'm still not 100% sure - but maybe this idea will get us closer to where your boss wants to be ... is this along the lines of what you're looking for? ...

[JeffKiper 9]

Sorry for the delay that is exactly what I am looking for.