Logix 5000-main task or multiple?

dginbuffalo

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Hello all. I am working on a project that has multiple skids which are almost identical and am thinking about creating multiple tasks for ease of use when trying to decipher the program. Are there any pluses or minuses for doing this? I could just have multiple routines running in the main task but it seems like I could have a better layout if I break each skid into its own task with it's own routines. When you do this- do you still need multiple JSR instructions to step through each routine? Thanks for any advice.
 
Hi

If it was me I would use a few tasks and break it out. Now I would think it will add a little time to your total scan but nothing that should affect anything. You will still need to create routines and and have a main which you will then also need jsr instructions in each task.
What plc are you using as this would also tell you how many tasks you can have.
I sooks times use tasks as if they were different plc processors even if they are in the one processor

Donnchadh
 
I think maybe you are confusing Tasks with Programs. Yes, breaking your logic up into multiple Programs probably makes sense.

Programs are a means of organizing routines and possibly tags. Tasks are a means of scheduling what order programs run and when they run.

You still use JSRs to call the routines within each program.

OG
 
Hi

Sometimes I use programs also but sometimes like if was a number of different skids I would use different tasks

I don't think either is right or wrong

Donnchadh
 
Tasks and Programs are not the same thing. There is a difference.

Use a task when you want to trigger logic to run based on one of the following:

  • Continuously. All programs in the continuous task runs each scan. Only one continuous task is allowed.
  • Periodically. Use this type of task to trigger logic to run at a specific timed interval (such as every 50ms). A Periodic task runs one time only for each timed interval. Multiple Period tasks are allowed.
  • Event Driven. When a specific event occurs, trigger the logic to run one time only until the next event.
Bear in mind that only the logic in the continuous task runs each scan. The other types are "triggered" and only run once per trigger. That may not be acceptable for a continuous process.

You can organize your logic routines within each program. You could have as many as 100 programs within your task. Each program could represent a specific skid, other piece of equipment, or a step in your process.

Programs make a lot of sense if you have several pieces of similar equipment.

OG
 
OG nailed it, Donnchadh confused it, I'm sure he didn't mean to....
 
On topic, has anyone else realised the similarity between the "program" context in Logix5000, and how a PLC5 or SLC is configured?

Each Logix5000 "program" has a "MainRoutine" (LAD File 2 in PLC5/SLC), and each "program" has its own data storage area.

To me, that "Program" area in a Logix5000 system looks just like the equivalent of a single PLC5 or SLC processor... and we can have 100 of those !!
 
That was actually how I used to describe programs. I would say that each program is sort of like an independent PLC with it's own routines and even tags. I stopped using that analogy, but it still pretty much holds true.

OG
 
"About 200 digital I/O and 24 analog inputs". Sounds like a perfect time to create one routine for the Digital IO and have the 200 different IO's index through that one routine. Same thing for your analog IO. This is assuming the functionality of both the digital and analogue are the same.
 

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