Controller/program scoped tags and network

Hi,
I'm pretty new at this but completed my first control job here recently and everything worked fine. I was programming for a CompactLogix PLC and I used RSLogix5000 to do the logic. Most of my code used program-scoped tags but I used a few controller-scoped tags so that a couple tasks could share them.

The automation guy at the plant said he wanted to do the HMI and tie in the new PLC to their network. So, of course I let him. Now he says he cannot access the program-scoped tags over the network and wants me to change them all to controller-scoped.

He is using an ethernet connection to the PLC. Is this correct that he will not be able to access these program-scoped tags via their network? Can anyone explain why? Or if it's not true, what needs to be done to access them?

Thanks
John

I forgot to mention. The HMI software in use is RSView 32.

Hello,

In PeakHMI to access program scoped tags the program name is prefixed to the tagname and a colon separates the two.

<program name>:<tag name>

Motor_1:Running

Controller scoped tags is only the tagname.

RSView32 generally uses RSLinx Classic as an OPC server to communicate with ControlLogix, so usually looking at the Tag Browser window.

An excerpt from RA Knowledgebase Answer ID # 52808:

Program scoped tags can be browsed, but they don't show up by tag name in the normal left hand pane of the tag browser. What you will see instead on the left side is a folder labeled "Program:<program name>".

If you highlight this folder, the tags defined in that Program tag database will then be available in the right hand pane. In the case of UDTs and array tags, there will be a sub-folder beneath the Program name as well.

Since the tags are listed alphabetically, these "Program:<program name>" listings will be mixed in with the Controller scoped tags that begin with "P" on the left hand side and can be very easy to overlook if you aren't expecting to find them there.

Thanks! Does RSView32 take the same approach with CompactLogix, as it does with ControlLogix?

Please excuse my ignorance... but let me just ask for a summary. This sounds like it means that anyone making an HMI out of RSView32 should be able to access my program-scoped tags, without me changing them all to controller-scoped. Am I correct? Does it matter what communication method they use to talk to the PLC?

Thanks again,
john

From a tag access perspective, all "Logix 5000" family controllers, including CompactLogix and ControlLogix, work the same.

You are correct that RSView32 can access Program-scope tags without any changes to the ControlLogix program or database.

I was specific about RSLinx Classic OPC because that's the most common method to connect RSView32 to a ControlLogix. 99% of the connections over Ethernet between RSView32 and ControlLogix use RSLinx Classic OPC.

There are a handful of other methods, including third-party OPC servers and old legacy network emulation, and I am always careful to not exclude unusual exceptions. If your application uses one of those unusual methods, the answer changes.

OK... round two.

I'm told that RSLinx Classic is running in a remote OPC configuration, meaning the HMI software does not reside on the same PC as RSLinx. And therefore the software does not allow remote OPC browsing. The way it sounds, it may be that they are not running RSView32. In any case, if the software does not allow remote OPC browsing, how can it communicate with the controller tags?

I'd appreciate some more input here.

Thanks

You are correct that Remote OPC is the configuration where the OPC Server (RSLinx) and the OPC Client (RSView32) are on separate computers.

In my experience, using Remote OPC versus Local OPC does not affect the way the tag browser works. I cannot imagine that it would affect the browsability of Program-scope tags without also disabling the ability to browse all tags.

There are some third-party HMI products that cannot address Program-scoped tags, but those are all using their own drivers. Anything that uses OPC should be able to browse and read any Controller-scope or Program-scope tag in the ControlLogix.

I guess if the "HMI guys" aren't going to be forthcoming about their software, there isn't a whole lot you can do to help them. I'd hate to see them continue to be convinced that they can't use Program-scope Tags.

I'm always cautious about saying "of course you can do that" when somebody says a function doesn't work. It usually results with "but I have version 2.10 with a limited-functionality demo license running on Windows 98 with an unpatched IIS, and RA Knowledgebase Document ID #12356 clearly says that disables the spellchecker, so what do you have to say about that, smart guy !?".

Haha. I guess you're expected to be a prophet of all things computer/controls related! I really appreciate your comments. I am going to ask one more question to see if I can get at any more info about the HMI. Otherwise I guess I will take some time to change these tags. They're small programs and it's not worth digging much further.