CCW program organization

[CJHoward]

I worked in a place with an old Modicon PLC. There were 8 blenders for storing plastic pellets. The PLC program was written in such a way that each blender and associated equipment were in their own "networks" Different functions (Make, Blend, Purge, Transfer) were defined (I guess) in their own network as well. So if you wanted the 2nd blender to transfer the command to position valves, turn blowers on, turn blowers off, etc were called from the Transfer network to monitor the inputs & affect the outputs of the 2 blender network.

As a technician troubleshooting a problem I knew I would start in 2 blender network, then go to the Transfer network & there was a function in the program where I could jump to whatever network I was looking for.

That was then. Now, I'm having to write a program for a Micro820. But there doesn't appear to be any "networks." I can write everything as one long program. I'm thinking I can do that, but I have to make sure to keep everything organized.

However, I see that I could write subroutines & that sounds like a better solution. Is that the "normal" convention for writing programs for the Micro800 controllers?

If I were called out on a job & I'm trying to figure out what a particular program is doing, can I expect to see a subroutine for "unloading" if it were a compressor or hydraulic unit? Or is it more normal just to write everything to a single large program?

 

[Old Man]

I don't understand what you mean by "Networks", I can't believe that each process (Make, Blend, Purge, Etc..) would have been on different networks. That would (In my opinion) make the complete program extremly difficult to write and manage.

This is how I organize my programs into different functions.

 

[CJHoward]

The rungs of the program were grouped into a "network" So it's really just a section of the code. Siemens does the same thing. Like a chapter in a book.

But in the Modicon program I could say, "goto network 54" & the editor would skip to network 54. We also had the program printed (dot matrix) & I would flip to the pages of the network I was looking for.

 

[CJHoward]

This is how I organize my programs into different functions.

Yes, that's what I was thinking, thank you.

 

[drbitboy]

IIRC every program under that [Programs] tree branch is unconditionally executed (called) each continuous scan cycle if they are scheduled with the continuous task (i.e. Not scheduled with a timed interrupt task), but it's been awhile and I am not sure about that.

 

[CJHoward]

IIRC every program under that [Programs] tree branch is unconditionally executed (called) each continuous scan cycle

That sounds right. I just wrote a small program with two routines. It seems to work the way you're saying. I just need to think ahead so that local variables are local & global variables are global.

Thanks for your help.