Rockwell Automation Logix5000 Controllers I/O and Tag Data Programming Manual - Manual (Page 31)

Organize tags Chapter 2
Guideline Details
Using extended properties in logic (continued) • Array Tags are constrained
A constraint on array tags applies if the array tag uses indirect addressing to access limit extended properties. If
an array tag is using indirect addressing to access limit extended properties in logic, the following conditions
apply.
− If the Array Tag has limit extended properties configured, the extended properties are applied to any array
element that does not explicitly have that particular extended property configured. For example, if the
MyArray has Max configured to 100, then any element of the array that does not have Max configured inherits
the value of 100 when being used in logic. However, it is not visible to you that the value inherited from
MyArray is configured in the tag properties.
− At least one array element must have specific limit extended property configured for indirectly referenced
array logic to verify. For example, if MyArray[x].@Max is being used in logic, at least one array element of
MyArray[] must have Max extended property configured if Max is not configured by MyArray. If this is not
done, if you attempt to access Max in logic on MyArray in logic, the routine does not verify.
− Under the following circumstances the software uses a data type default value:
− Array is accessed programmatically with indirect reference.
− Array tag does not have the extended property configured.
− Member of array does not have the extended property configured. For example for Array of SINT type,
when max limit is called in logic for a member, the value 127 is used.
• Removing Extended Properties
You cannot remove extended properties that are accessed in logic when the project is online with the controller.
The Max and Min check boxes in the Extended Properties box in the Tag Properties pane are unavailable.
You have to go offline to remove the extended properties.
Removing extended properties in logic on structure tags is unavailable at the tag level. For example, if MyUDTTag
has 2 members, Mem1 being a DINT and the Mem2 being a SINT, if you define limit extended properties in Logic
on both members, but are only accessing Max extended properties on Mem1, the Max check box is unavailable in
Extended Properties for both members. You are not able to remove the Max extended properties for
MyUDTTag .Mem2 online.
The same applies for Array tags. If you define limit extended properties on an array element and that element is
accessed in logic, then you cannot remove the limit extended properties from any of the array elements.
The Tag Editor lets you create and edit tags by using a spreadsheet-style view of
the tags.
Important: The Logix Designer application also automatically creates tags when you:
− Add an element to a sequential function chart (SFC).
− Add a function block instruction to a function block diagram.
Follow these steps to create a tag by using the Logix Designer application.
Create a tag
Rock well Automati on Publication 1756- PM004E -EN-P - October 2014 31