Referencing Program tags outside program folder scope

I was looking at a Studio5000 PLC file as reference, and noticed the "standard" for this job used was using program tags for each program folder, but it was also using this program tags outside of this scope inother program folders. I was surprised since I did not know you could do this. To do this you have to type the tag with a backslash + name of program folder + dot + local tag name, like this:

\Sys.Auto

if its a safety local tag it would be \sSys.Auto.

My question would be, does anyone know what manual or part of the rockwell literature I can read more about this topic, was this a recent feature added or has it always been there?

I believe what you are seeing is "parameter" tags. This is a feature that was added with version 24. Program tags were renamed to Local tags and these parameters were added. When you look at the Local tags, you can see which tags are Local and which are parameters.

OG

After some quick testing here in v34, the \... syntax grants you access to the other program's parameters, but not its local tags.
For more info, see:
https://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm021_-en-p.pdf

These are "Public" parameters: local tags to a program, but in creating the tag, the Usage dropdown has the option of "Local", "Input", "Output", "InOut" and "Public".

Using "Public" allows other programs to access the local tag using the syntax the OP described: \ProgramName.PublicTagname

It's a great technique for having two programs that are "the same" yet independently having to write tags to a third program differently without using the Alias trick of having the two programs have the same tag name but alias different Controller-scoped tags.

I think it came out in v.28 or so. That's when I first started using it.

I think that, with this, it would be possible to create an Event task with a single Program, write some values to its Public tag, trigger the Event, read other values, and essentially have an AOI that is editable online.

I've never taken it that far, but I think that's where Rockwell is trying to head.

Thanks for all your replies. This is what I was looking for. I will read more on this topic, as someone who works a lot with customer templates, I had not seen this feature implemented before, until now.

A couple comments referred to "Public" parameters. As you read up on parameters, you will see there are different types.

A Public Parameter in Program A will automatically appear in your tag browser even when you are in Program B. This is somewhat similar to Controller tags.

You can also create Input Parameters, Output Parameters, and InOut Parameters. If you create one of these parameter in Program A, you will not automatically see it in Program B. But, while in Program B looking at the tag browser you can select to view parameters from Program A. So any of these parameters can be used in another program.

OG