
Chapter 2
CIP Services and User-created Tags
50
Rockwell Automation Publication 1756-PM020F-EN-P - January 2019
The Template object contains information about structures and many
instances of the object class created to hold structures associated with data
inside the Logix 5000 controller. When creating new user-defined types
creates a new instance of the object class. The instance ID numbers do not
follow any order.
Structured tags are linked to the template object instance through the Symbol
Type attribute. For this reason, it is not necessary to read all the instances of
the Template class. Simply view the Symbol Type attribute. When Bit 12=0;
Bit15=1, then Bits 0-11 represent the instance ID of the template associated
with this tag.
For example, assume a
MachineSummary
tag exists in the controller the tag
is a structure of type STRUCT_B. The Symbol Type attribute (attribute 2)
for this tag has the value 0x82E9. Bit 15 is set, indicating this tag is a
structured tag and Bit 12 is reset so it is not a reserved tag. The value of bits
0-11 is 0x2E9 is the instance ID of the Template object where the structure
makeup of the tag is defined and the value is in the range of values that are
accessed.
Use instance ID 0x2E9 in the Step 3 example to retrieve the structure
information for a tag of this type.
After gaining an understanding of interpreting the Symbol Type attribute,
identify tags that are not user-created from those that are user-created.
See also
Step 2: Isolate user-created tags from system tags/identifying
Beginning with the full list of symbol instances, eliminate tags that should
not be accessed or manipulated by applying the following rules.
1.
Discard tags that are not in these ranges (eliminates Predefined and
String)
•
The Symbol Type, Bit 12=0, Bit 15=0, and Bits 0-11 range from
0x001-0x0FF (atomics)
•
The Symbol Type, Bit 12=0, Bit 15=1, and Bits 0-11 range from
0x100-0xEFF (structures, not including Predefined)
2.
Discard tags that contain
these characters
Eliminate tags by applying rules