Add on Instruction

Hey guys,
I just uploaded the program out of one of our machines and it has add on instructions as buffers for the inputs and outputs. I'm confused as to the purpose of these. I know about the asynchronous scan of the compact logix and I always just write a line of code (input xic to internal ote) to cover that. This is the logic and the AOI:

What does the logic in the AOI look like?

The AOI is providing additional functionality, albeit very minor. Given that set/reset, enable/disable inputs are included it looks like it provides additional control. Set/reset I would interpret as a force on/off, possibly for simulation purposes. The enable/disable could simply be some type of configurable option, or a possible check from an alarm perspective.

The AOI provides additional members for each input to utilize:
I_100.Real_In
I_100.Buffered_Out
I_100.Enable
I_100.Disable
I_100.Set
I_100.Reset
I_100.Raw
I_100.Value

Anytime you add a new input, you inherit these additional members which are available for control elsewhere.

This AOI provides additional functionality over your simple XIC OTE buffering solution. Whether or not it's actually needed, you'd have to see if the tags are referenced anywhere else in your program.

Ok. I could see what it was doing as far as the logic, I just didn't see the purpose of it. He also buffers the outputs in a similar fashion. I don't think it's necessary in this program. It's not a very complicated program and I don't see anywhere that any of the tags are referenced, beyond the normal use as an XIO or XIC.

JRoss said:

What does the logic in the AOI look like?

Click to expand...

The logic for the AOI is right above it in my original post

T Gibbs said:

Ok. I could see what it was doing as far as the logic, I just didn't see the purpose of it. He also buffers the outputs in a similar fashion. I don't think it's necessary in this program. It's not a very complicated program and I don't see anywhere that any of the tags are referenced, beyond the normal use as an XIO or XIC.

Click to expand...

Most likely a 'standard' method for this programmer then.

That's what I'm thinking. I'd never seen it done that way and it confused me at first. Thought maybe he knew something I didn't.

There is probably some HMI dingus that allows the inputs and outputs to be molested using the interface provided by the AOI

Geoff White said:

There is probably some HMI dingus that allows the inputs and outputs to be molested using the interface provided by the AOI

Click to expand...

No, there's no HMI on this. It actually is tied into another machine, which has no PLC, and just works off signals from it and photo eyes. There's no manual controls at all to this.

Someone has a standard set of abstractions they use for everything. Probably from a process control background where they have lovely HMI stuff to interact with it.

Geoff White said:

Someone has a standard set of abstractions they use for everything. Probably from a process control background where they have lovely HMI stuff to interact with it.

Click to expand...

Yea, that's what I'm thinking