Writing to Logix datatype Book_STRING

Ignition
1

I am unable to write to a Book_STRING datatype in an AllenBradley ControlLogix PLC.
I have configured a tag in ignition with datatype “Automatic” and am able to read the value of the PLC tag, but am unable to write to the tag. I get:

Error writing to tag FormulaNotes Bad; unspecified.

I have also tried writing to this tag using system.opc.writeValue, and get the same error message.

Is this datatype not supported (for write) in the OPC UA server?
Is there a way to add this to the list of supported OPC UA server datatypes?

I also tried to write to the Book_STRING’s member DATA which is an array of 520 SINT’s, but that didn’t work either.

2

What version of Logix is this? As far as I am aware Book_STRING isn’t a built in type for Allen Bradley, this sounds like a UDT within the PLC.

The STRING type’s DATA member is only an array of 82 SINT’s.

You might also insure that your string is encoded to UTF-8 or lower so there isn’t a chance for an overflow.

3

I’m using RSLogix version 32. The Book_STRING type appears under DataTypes\Strings.
Maybe it is a user data_type but just appears in a special folder for strings.

So assuming it is a UDT, is there a way to configure ignition to be able to write to it?

4

It appears that someone has created a string type that will hold 520 characters. It’s probably dependent upon what that particular tag is being used for. It isn’t the default STRING type, but a user defined STRING type.

I wouldn’t think that Ignition would have any issue writing to this type.

The External Access of the tag doesn’t happen to be set to Read Only?

Outside of that, maybe @Kevin.Herron might have some Ideas.

5

Yeah, I would have expected this to work.

6

@rsonnicksen Try increasing the CIP Connection Size setting for that device connection to 750 or 1000.

Writing to Strings larger than the connection size got implemented at some point but maybe you’re on an older version.

edit: support for writing Strings larger then the CIP connection size was implemented in 8.0.15.

3 Likes