I/O to Tagname

ABGreen

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Join Date
Sep 2008
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PA
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I am new to using tagnames for plc programming. How do I find what tagnames are tied to for real world i/o in an existing RSLogix 5000 PLC?

Also, How would I search used and unused I/O points in this 5000 processor?

This is a flexlogix controller.

Thanks,
ABGreen
 
Last edited:
Typically, although not always, we use Aliases for I/O.

So, the automatically generated "Base" Tag of something like: Local:2:.I.Data.5 would mean, Local chassis, slot #3, Input data point #5

You could then make an "Alias" tag which is a *new* tag that you can name as needed for your application and point that tag to the "Base" tag for it's data. So in your program you could use the name "Pump_Start" as an alias to that base tag.

If you open the tag window and sort by the "Alias For" column you can track down what Aliases are tied to what Base tags. Also, on the tag window is a "Show" option where you can filter. From there you can select "Unused Tags". This would show you tags that you have created aliases for, but have not used.

OG
 
Last edited:
Example

Thank you for your help. Here is what I am seeing in the controller that I am trying to work with.

Tagname: DI_PB_UT_Off
Alias for: DI_01_00.3(C)
Base Tag: DI_01_00.3(C)

My guess is that this is a discrete input card located in card 1 (second slot) of the local bus, data point #3. I expected the alias and the base to be different.

What is the (C) for at the end?

Thanks in advance!
ABGreen
 
hi,

it looks like there are 2 aliases used. check if DI_01_00.3 is also an alias for something else.

I think you have to check for DI_01_003 only. I am sure this is an alias for a real Input or Output.

greets
 
Tagnames

How would I go about digging deeper for an alias within an alias to get to the base tag for that alias?

I need the automatically generated base tag to find out where the tag is being used as the real output or input.

I also need to find a way to look at all the I/O points that are unused, it does not seem intuitive with tagnames.

Thanks again for your guidance!

ABGreen
 
It IS possible to have an alias to an alias, but that is NOT what you have since the "Alias For" and "Base Tag" fields both show the same thing. An alias to an alias would have different tags in those two fields.

What you could have though is an alias pointing to a memory location instead of a I/O module. In other words rather than doing a standard alias, the programmer may be using the logic to perform a similar end result. They are likely moving the data from the default tag into the tag name you are seeing and then for some reason aliasing that.

So, the "(C)" you are seeing in the name is just telling you where to find the Base Tag. DI_01_00 is found in the Controller Tags section rather than in the Program Tags. The ".3" is bit #3 in that tag.

You need to find DI_01_00 in the Controller Tags and then you should Cross Reference it to find out where it is coming from. When you find it in the Controller Tags, right-click on it and select Cross Reference. In the window that opens look for a row that lists the exact tag you are looking for and then look at the column titled "Destructive". You want the one that has a "Y" for your specific tag. Double-click on it to jump to that location.

OG
 

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