# OPC-UA - CompactLogix - Device connectd but unknown tag Qual **URL:** \ **Category:** Ignition\ **Created:** [August 9, 2016, 7:24am UTC](https://forum.inductiveautomation.com/t/opc-ua-compactlogix-device-connectd-but-unknown-tag-qual/12016 "2016-08-09T07:24:20Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![nminchin](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nminchin/32/6911_2.png) [@nminchin](https://forum.inductiveautomation.com/u/nminchin)\ **Post date:** [August 9, 2016, 7:24am UTC](https://forum.inductiveautomation.com/t/opc-ua-compactlogix-device-connectd-but-unknown-tag-qual/12016/1 "2016-08-09T07:24:20Z")
Hi, I’m new to Ignition and trying to read tag data from an AB CompactLogix PLC. The device is configured and connected, however when I browse tags from the OPC browser, add some into the Ignition Tag database, their OPC quality is Unknown and the values cannot be read. If I try to write to the tag however, I can see that this is written into the PLC. How can I diagnose this issue? Is there a diagnostics window somewhere for tag-related issues? Thanks in advance. Regards, Nick More info on error when testing reading using the inbuilt OPC client in the gateway webpage: Read completed. [Ignition OPC-UA Server]ns=1;s=[CompactLogix]Global.B01.Man Status: Bad\_CommunicationError Value: null Quality: [Bad\_CommunicationError] A low level communication error occurred. Timestamp: 8/9/16 5:10:45 PM ACST ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [August 9, 2016, 11:44am UTC](https://forum.inductiveautomation.com/t/opc-ua-compactlogix-device-connectd-but-unknown-tag-qual/12016/2 "2016-08-09T11:44:06Z")
Rockwell made major changes to the tag access protocol in firmware version 21 and above. Inductive Automation wrote a new driver to deal with the changes. What you are describings sounds like the old driver trying and mostly failing to talk to the new firmware. You haven’t provided enough information to be sure, but you probably need to delete the device and re-create it with the correct driver. ---
**Author:** ![nminchin](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nminchin/32/6911_2.png) [@nminchin](https://forum.inductiveautomation.com/u/nminchin)\ **Post date:** [October 25, 2016, 7:13am UTC](https://forum.inductiveautomation.com/t/opc-ua-compactlogix-device-connectd-but-unknown-tag-qual/12016/3 "2016-10-25T07:13:12Z")
Thanks Phil, I’d say this would be the issue, can’t test it at the moment though. However I’ve had issues with this in another SCADA package as well, it didn’t even cross my mind for Ignition though. Cheers ---
**Author:** ![joelt](https://avatars.discourse-cdn.com/v4/letter/j/9f8e36/32.png) [@joelt](https://forum.inductiveautomation.com/u/joelt)\ **Post date:** [September 2, 2020, 8:47pm UTC](https://forum.inductiveautomation.com/t/opc-ua-compactlogix-device-connectd-but-unknown-tag-qual/12016/4 "2020-09-02T20:47:45Z")
I’m having this same issue but communicating to ControlLogix v20. Any ideas? ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [September 2, 2020, 8:54pm UTC](https://forum.inductiveautomation.com/t/opc-ua-compactlogix-device-connectd-but-unknown-tag-qual/12016/5 "2020-09-02T20:54:35Z")
The V21 driver can talk to V20 as well, but with substantially reduced performance. If you’ve upgraded the firmware to one of the later V20’s that cuts off the legacy optimizations, it is your only choice. Consider upgrading your firmware out of that dead zone.