OPC server can't sync read from PLC, but it can sync write successfully

Hi,

I'm working with a Citect OPC DA server and an Allen Bradley ControlLogix L71 PLC. I have set up my boards, ports, and I/O device. When I test communications with an OPC Client, I can't seem to do a sync read. But I have confirmed with Studio 5000 that I can do a sync write successfully. I do get an error code of 0x80004005 which I believe is an unspecified error. I have redundant servers, but the result is the same on both of them.

All firewalls are disabled. I also have a CompactLogix that works perfectly. I'm running out of ideas to diagnose the issue. Does anyone have any questions or suggestions? I have full administrative access to all of the network switches between the two devices and I can ping the PLC from the server.

Thanks,
David

Try using:
https://opcexpert.com/

widelto said:

Try using:
https://opcexpert.com/

Click to expand...

Wow... never heard of this one. And it's free? Anyone care to share any history?

I am using two different OPC servers now (have been for the last 5 years), and in the process of adding another, and the new one is not exactly playing nice.

Thanks in advance!

I tried OPCexpert and there seems to be compatibility issues with it on our systems. We are running Windows 10 x64. I tried changing the compatibility settings and running as an administrator.

Further help can be found at :

http://www.opcti.com/whitepapers.aspx

http://www.opcti.com/Video-Tutorials.aspx

Ops...nevermind. It won't run off a network drive. I moved it to a local drive and it works. I will try it out now.

So I tried out OPCExpert. I am comparing two tags that were made using the same user defined datatype on two different Allen Bradley PLC's. TI8005_sPV is the good one:
https://www.dropbox.com/s/wyotkvtewblpakj/TI8005_sPV.jpg?dl=0

CR001_MI_sPV is the bad one:
https://www.dropbox.com/s/sk9azv35wqorpbg/CR001_MI_sPV.jpg?dl=0

You can see the error below 0xC0040004 indicating that the server cannot convert the data between the requested data type and the canonical data type. I don't know why; both tags are REAL in the PLC and REAL in CitectSCADA. I can write to the bad one, so I know the data is going to the correct PLC. I suspect that the server isn't getting the initial data for CR001_MI_sPV from the PLC, which is why it thinks the datatype isn't convertible.

So, an update. I found some problems in the equipment template XML files for tag generation in CitectSCADA. I removed a mystery line and added a missing Semicolon on a spreadsheet we use and now some of the tags can be read. It seems now the problem is by equipment template. The information that was missing in our tag database ultimately was the raw min/max, the engineering min/max, the units and the format.