Rockwell Automation Publication 1756-PM004D-EN-P - September 2012 47
Organizing Tags Chapter 2
Address Tag Data
A tag name follows this format.
Name [Element] .Member [Element] .Bit
or
.[Index]
= Optional
Where Is
Name Name that identifies this specific tag.
Element Subscript or subscripts that point to a specific element within an array.
·Use the element identifier only if the tag or member is an array.
·Use one subscript for each dimension of the array. For example: [5], [2,8], [3,2,7].
To indirectly (dynamically) reference an element, use a tag or numeric expression that provides the element number.
·A numeric expression uses a combination of tags, constants, operators, and functions to calculate a value. For example, Tag_1-Tag_2,
Tag_3+4, ABS (Tag_4).
·Keep the value of the tag or numeric expression within the dimensions of the array. For example, if a dimension of an array contains 10
elements, then the value of the tag or numeric expression must be
0…9 (10 elements).
Member Specific member of a structure.
·Use the member identifier only if the tag is a structure.
·If the structure contains another structure as one of its members, use additional levels of the.Member format to identify the required
member.
Bit Specific bit of an integer data type (SINT, INT, or DINT).
Index To indirectly (dynamically) reference a bit of an integer, use a tag or numeric expression that provides the bit number.
·A numeric expression uses a combination of tags, constants, operators, and functions to calculate a value. For example, Tag_1-Tag_2,
Tag_3+4, ABS(Tag_4).
·Keep the value of the tag or numeric expression within the range of bits of the integer tag. For example, if the integer tag is a Dint (32-bits),
then the value of the index must be 0…31 (32-bits).
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