We have a Testbed PLC and a Production PLC … both use the Logix driver. Production PLC is older version thatn Testbed PLC. I had two tags defined … one is a boolean, one is a float.
I created one device. The IP address pointed to the Testbed PLC
I bound the tags to the device.
I then changed the IP address of the Device from the one that corresponds to the TestPLC to the ProdPLC.
The Boolean tag? reconnected fine.
The Float tag? Didn’t reconnect … got “bad_ConfigurationError”
I exported the path as a reference.
Then I edited the tag, confirming the path was correct …
The tag then responded properly … no quality errors, read the values, etc. etc.
I exported the path … and it hadn’t changed.
But … obviously … something had changed when I re-edited the tag … it was not connecting properly and then it was connecting properly.
Is there some kind of re-initialization? Is there a way to predict which ones will reconnect and which ones won’t? I’ll be changing from TestPLC to ProdPLC often enough that this is going to be a risk I have to manage somehow.
Note … this is the system that I was discussing in this other post (link) … I have NOT attempted to use the hosts file to manage the switching back and forth between TestPLC and ProdPLC … yet
Is one PLC in a pre-version 20 firmware and the other in a post-version 20 firmware?
You have to use the legacy driver to talk to Logix PLCs that are pre-version 20. Also, the device paths aren’t the same for tags using the legacy driver vs tags using the post-20 driver.
EDIT: Assuming your connection is working going to the production PLC, try dragging a tag that you already have defined. Do the device paths look the same?
Thanks for the reply.
The ProductionPLC is an older version (rev 20.19) from the TestbedPLC (rev35) … but … I didn’t have to change to the Legacy driver … simply re-editing the tag did the trick. From the description of the Legacy Logix, it is NEEDED for up through 20.18 … so this one is JUST past that.
So … I didn’t think we HAD to use the Legacy driver … and having the driver (and tag path) the same as the testbed vs. production made switching back and forth easy)
Yes, you’re on the very fringe of where you can do that. It’s kind of a gray area with AB PLC versions and you can have funny behaviors.
Another notable thing… If you’re using Linx Gateway to read your tags and referencing that as an OPC server from Ignition then the tag paths stay the same regardless of firmware version. Another upside is that Linx Gateway using Rockwell secret sauce behind the scenes to read tags much more efficiently than the OPC standard they release for other companies to build Rockwell drivers from.
IA’s AB drivers are good but they’re built to the official standard Rockwell releases which is unfortunately not as fast as what Rockwell uses for Linx Gateway because linx gateway is using undocumented API calls behind the scenes.
A downside is that it is an added cost.
We tend to use Linx Gateway on systems that are reading 30k or higher tags from Rockwell PLCs. Systems that large can justify the added cost and the performance impact is significant in some situations.