CIP Services and User-created Tags
44 Rockwell Automation Publication 1756-PM020F-EN-P - January 2019
See also
CIP Services and User-created Tags on page 41
How tags are organized in the controller on page 41
Client applications access atomic tags or atomic members of structured tags
by:
• Identifying the name of the tags for accessing
• Learning what tags are present in the controller and enabling users to
select the desired data.
Tip:
In certain scenarios, it is not necessary to read all symbol instances or interpret template information. For
example, if the name of the tags are recognized and the Symbolic Segment Addressing method is used to
access only atomic tags or atomic members of structured tags, it is not necessary to read all symbol
instances or interpret the template information.
Client applications identifying the available tags or accessing structures must
identify the required tags for access before manipulating tag data. This
information is used to identify the data type of each tag and enable the
application to interpret the data value associated with the tag.
Update the list of information as required. User program changes frequently
create or delete tags, and add, delete, and modify user-defined data types.
This procedure:
• Creates and maintain a list of controller-scope symbol objects in an
Logix 5000 controller
• Associates each instance with a template object instance if it is a
structured tag
• Eliminates the symbol instances of data that the client application does
not access or manipulate
To create and maintain a symbol object list:
1. Find all controller-scope tags.
2. Isolate user-created tags from system tags.
3. Determine the makeup of the structures. Structure members are not
separate Symbol instances.
4. Determine the data packing of structure members in a message.
symbol object list
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