OPC-UA SLC Incomplete Datatable read

Starting to setup new project and i am laying out all my tags. Started with Inputs comming straight off NI8 cards. These are in a SLC 13 slot rack. I have everything working fine up to slot 7 then OPC wont read any values past slot 7. It is not reading them in the designer or in the quick client on the gateway. I have checked all items past I:112 and nothing is reading. Any Ideas?


I think the problem is that the Ignition driver does not support reading values directly from analog or other modules that have multiple words. Reading word 0 will work, but reading any other words above word 0 will not read correctly. The only way to accomplish reading these words using our drivers is by using a MOV or COP ladder logic instruction to move the analog or other values to N or other memory type that can be read by our drivers.

To read words from modules we would need to know the type of module. Currently we do not have a method to read this information directly from the processor. In the future we may add a configuration section that allows for defining the I/O racks in Ignition, but currently it is not on the road map.

Well actually it does work correctly for the first 7 cards in the rack. Im doing it right now. I can read all 8 words from each of the first 7 cards but nothing past that. The first 9 are NI8 cards then slot 13 we have IA16 cards which it will not read even the booleen values. Just odd why part of them read and part didnt.

The AB drivers optimize the reads. In other words it groups like addresses into one request instead of separate requests. For example I:2/00, I:4/15 and I:5/12 are all grouped into one request. This is done to minimize the number of requests which improves speed and reduced workload on the processor.

What happens is if one address in the the request is invalid such as I:4/15 is not valid, then the whole request will fail. I:4 maybe invalid because the it is an output module instead of an input module.

Have you verified that the value of each word is correct? You will find that I:2.0 will be the correct value and I:2.1 through I:2.x will not be correct.

This is a known feature that is not supported by the Ignition drivers.

I have verified that the values were correct. I am currently in the process of mapping all of the IO into seperate datatables in each PLC and will get the info that way. Since the direct IO reads are not supperted in Ignition. Thanks for the info.