RSView32 and DDE problem.

[imloggedin]

I have been designing an HMI using RSView32 and DDE to RSLinx Classic. The problem im having is that when i created 2 tags in the tag database, if both of these tags reference the same address in the PLC then they both freeze up and stop working. if I delete 1 of them or the graphic associated with it, it starts working again. But as long as 2 tags reference the same plc address, they both die.

Any solution to this problem?

 

[imloggedin]

I just tried switching my Node to OPC instead and it works fine on that. Any downside to switching my node to OPC and keeping the tag database exactly how it was?

 

[Mickey]

Not an ansewer to your question, but why are you creating two tags with the same address? You should be able to use that one tag on multiple screens.

 

[imloggedin]

Long story, but I have to do it that way, no way around it.

 

[robertmee]

Long story, but I have to do it that way, no way around it.

What's the story? If you need two tags to represent the PLC address, create one I/O tag and one memory tag and use derived tags to assign the I/O tag to the memory tag. You really shouldn't have two tags pointing to the same I/O address.

 

[imloggedin]

What should be wrong with having 2 reference the same? OPC/DDE isnt smart enough to assign the value to 2 tags instead of 1? That would be a horrible protocol. Im not writing to the tags, just reading.

 

[OkiePC]

There should be no problem having two tags reading the same PLC address. I have seen this done without any issues using direct drivers (both DH+ and serial DF1). RSLinx should recognize two reads from the same tag and only perform the read once as long as they're in the same scan class.

One useful reason to do this might be so that the tag could be scaled using two or more different methods. In most cases you would only want one scaled version of a PLC tag, so I can understand the statements made by Robert and Mickey.

I cannot imagine it would create an issue with a DDE/OPC driver either, perhaps it was a fluke or maybe we need an "Automation Therapist" to help us understand the specifics.

 

[imloggedin]

It definitely wasnt a fluke. I can make it happen over and over. When I switched to OPC its fine. It only did that with DDE. Is there a problem switching my node to OPC with the same addresses in the tag database (i dont wanna edit my whole database)?

 

[robertmee]

What should be wrong with having 2 reference the same? OPC/DDE isnt smart enough to assign the value to 2 tags instead of 1? That would be a horrible protocol. Im not writing to the tags, just reading.

There's a fine line as to what's possible and what's practical. There's alot I can do that's possible in a PLC/HMI setup, but under general circumstances, there's alot that's not practical. Don't take it as criticism....I'd just like to know under what conditions you feel that this is practical.

 

[imloggedin]

It is very practical in what im doing. I just dont feel like typing it all out. Im assuming the OPC and DDE tags are no different in the tag database? It seems to work ok.

 

[robertmee]

It is very practical in what im doing. I just dont feel like typing it all out.

Fair enough, but remember that those that are trying to help you fortunately don't share that attitude.

 

[imloggedin]

I appreciate those who helped me. I dont think my attitude is in anyway wrong, the whole popup screen / main screen thing i have going on would take way too long to explain, theres alot of VB script and whatnot which isnt really relavent to my question. You may think you can tell me a better way to do that, and bypass the double tag thing, but i cant change how it is now, so its irrelevant. Why spend an half hour typing out what I cant change anyway.

Like I said, Thanks to those who helped.

 

[robertmee]

I'm not picking on you, really, I'm not....

The reason it would be relevant is that it might help someone in the future. I'll be the first to admit that I don't know everything....Not even 1/10th of everything. So, if there is a situation where two tags are an elegant solution to a problem, I'd like to know that situation for my own learning. If you are knee deep in your problems now, that's fine...you don't have the time to explain. But, at some point, it could possibly be beneficial to many if you would explain the situation that prompted your question in the first place.

 

[Gil47]

I have read details of your post and wonder if this info may be relevant to your issue
Your setup of RSLinx, I believe is in one of those cache files.

Something I have posted before.

Just a different slant that may be worth trying.

Sometimes when edits are done in RSView 32, the project just does not want to release the cache files, and tries to keep running on previous settings.

A repair I do if any issue crops up, is to shut down the project, then in windows explorer, go into the project folder, open the projects cache folder, and blow away all files in that cache folder, they will be rebuilt on the next start up.

The next thing I do is go to the projects Tag folder, and look for one file with "the project name".cac
I THEN BLOW THAT ONE ONLY AWAY, leaving all the other files in that folder, this .cac file also will be rebuilt on project start up.

Then shut down computer and reboot and run your project.

I cant promise this will fix your problem, but it wont harm it either.