SLC 5/03 tags

I downloaded the logic from a 5/03 plc that we do not otherwise have the original programming for. This system also has a PanelView display.

Of course, there are no comments. So I have been going through it and figuring out what is what. No problem so far. Now I realize that the tags are not in the ladder logic either. What happens if I make a change and upload that to the plc? With no tags in what I downloaded, won't the PanelView stop working correctly?

I understand that comments are stripped out of what is sent to the plc to save space, but the tags have to be in there. So why don't they download with the ladder logic? Is there a way to get them to?
Dave

Nothing but the data table addresses ( like "N7:10" or "B3/12" ) are actually loaded into the controller, or accessed by an HMI.

The Rung Comments, the Address Descriptions, and even the Symbol database are entirely in the RSLogix 500 offline file and are not used by the controller or the HMI.

PanelView Standard terminals have their own little Tag database, but those Tag Names are entirely inside the PanelView. Every Tag that is related to an SLC data table element is linked to an ordinary Data Table address.

As long as you don't delete or change the size of a Data Table, the PanelView will continue to read and write the data tables of the controller correctly.

Tags arenot used in Logix5/500. The tag database is in the Panelview program and basically just maps a tag in the panelview to the a value in the data table on the PLC.

I may need to add to the data table, so I don't think it would take too long to copy the tags from the PanelView (maybe 40 or so) and put them in the ladder logic. Then I don't think I would have any problems. Correct?
Dave

No, there are not any tags in the ladder logic. The HMI Tags are completely separate from the PLC. THe HMI just reads and writes to the data files in the plc (B3, N7, etc).

Adding a data table will have no effect on the Panelview. However, replacing and deleting values can possibly effect the HMI if it is using those data table elements.

Assuming this is a Panelview and not a Panelview plus, it may be helpful if you fire up Panelbuilder32, upload your panelview program, and take a look at the tag database there and see how it just links to the data table.

Helliana said:

No, there are not any tags in the ladder logic. The HMI Tags are completely separate from the PLC.

Click to expand...

Hi, thank you for the response. I believe there is a place to put tags in the ladder logic. If you right click a variable and select "edit description", you get a description and a blank for "symbol" which I have always assumed (perhaps incorrectly) that that was the tag that had to match the tag in the HMI for the same variable.

It isn't necessary to put anything here? I thought you had to have this because there could be several plc's and several N7 variables.

JulianDave said:

If you right click a variable and select "edit description", you get a description and a blank for "symbol" which I have always assumed (perhaps incorrectly) that that was the tag that had to match the tag in the HMI for the same variable.

Click to expand...

You assumed incorrectly. The description and symbol fields are just a comment to tell the programmer what that data element is used for. The PLC doesn't use this information at all, which is why it is not there when you do an upload from the PLC.

JulianDave said:

It isn't necessary to put anything here? I thought you had to have this because there could be several plc's and several N7 variables.

Click to expand...

If you were using a tag-based PLC (such as a Controllogix), you could also have two tags with the same name across multiple PLCS so tag's don't help solve this problem. However, each PLC will have their own address or node on the network, so the HMI knows which tag/data elemement is from where.

SLC-500 Symbols are sort of a predecessor to Logix Aliases, because of the way they substitute for the underlying Data Table Address.

They're purely a convenience and efficiency tool for use by RSLogix 500.

Sometimes they were also used by other software that had its own databases (notably RSView), where the SLC Symbol and the associated SLC data table address was imported and had an RSView Tag created with the same name and the same associated SLC data table address.

This made the RSView Tag Database look a lot like the SLC-500 Symbol database, but this was only because one was used as a template for the other. The RSView software still natively used the data table addresses to access the controller memory.

Thank you both. Very eye opening. I had no idea.