AB I/O mapping

AB RSLogix5000

I have some RSLogix experience but am still very new. I have zero ethernet experience. I am trying to understand how the I/O is mapped within our systems. All I/O is ethernet based.

CPU > EN3TR(ethernet card in the rack) > 1756-ENBT/A with modules > devices connected to the modules (either I or O)

Ultimately, what I am trying to put together is a spreadsheet that correctly "maps" the inputs and outputs (as designated in our schematics)to the input and output tags that are in the program. Depending on how I connect to the controller, I may not see the tags so all I have is an address to go by.

Sorry if I am not using the correct terminology. I can follow the trail on systems that use I/O cards in the rack with the CPU. It is the ethernet configuration that has my brain all wonky.

There are many varied possibilities with Logix I/O over Ethernet. Do you have multiple controllers on the I/O network?

You will need to look at the controller tags and perhaps the I/O configuration of each controller to find out which one owns which I/O. From there, you can figure out if the tags are aliased or copied to other addresses (cross reference in RSLogix 5000) which may affect how or where you want to document them.

If you can post the affected .acd files you should get lots of help. If it's a single controller system, then it won't be too complex at all.

dkintz said:

Depending on how I connect to the controller, I may not see the tags so all I have is an address to go by.

Click to expand...

Please expand on that statement.... It shouldn't matter how you connect to the controller, you should still see the tags in the tag database. And it doesn't matter if you connect to your PLC via RS232, EtherNet, ControlNet, or USB.

Perhaps you are looking into Program tag databases, where you will not see your I/O tags. Logix5000 has a Controller (Global) tag database, and each Program has their own (Private) tag database.

Basics....

When an I/O module is created in the I/O configuration (and they have to be put there to be able to use them), the system automatically creates tags in the Controller-Scoped tag database to contain the data that is exchanged with the I/O module.

I/O tags look like Location : Slot : Direction

Location : The name on the I/O configuration of the communication module communicating the I/O data. In the same chassis as the controller, Location is always Local.

Slot : slot number of the I/O module

Direction : I = Input, O = Output. Both of these are from the controllers perspective - data coming IN to a controller will be I, data going from a controller (eg output data) will be O

Inside the I/O tags that are created will be sub-elements that contain the I/O channel fault status and actual I/O data.

These tags are the physical "addresses" that the system uses to exchange data with I/O modules, and some people are happy to write code that references these tags directly,

eg. Local:5:I.Data.19 (bit 19 of an Input module, in slot 5, in the same chassis as the controller.

More advanced is the idea that "alias" tags can be created that automatically "map" to the I/O points inside the I/O tags,

eg. Tank3_HI aliased to Local:5:I.Data.19

Alias tags can reside in any database, Controller, or Program scoped, but the I/O tags created by putting a module into the configuration will go into the Controller tag database.