Structured Text Components: Assignments
Use an assignment to change the value stored within a tag. An assignment has this syntax:
tag := expression;
where:
Component | Description | |
Tag | Represents the tag that is getting the new value; the tag must be a BOOL, SINT, INT, DINT, STRING, or REAL. Tip: The STRING tag is applicable to
CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | |
:= | Is the assignment symbol | |
Expression | Represents the new value to assign to the tag | |
If tag is this data type | Use this type of expression | |
BOOL | BOOL | |
SINT
INT
DINT
REAL | Numeric | |
STRING
(
CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | String type, including string tag and string literal
(
CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | |
; | Ends the assignment | |
The tag retains the assigned value until another assignment changes the value.
The expression can be simple, such as an immediate value or another tag name, or the expression can be complex and include several operators and functions, or both. Refer to Expressions for more information.
TIP:
I/O module data updates asynchronously to the execution of logic. If you reference an input multiple times in your logic, the input could change state between separate references. If you need the input to have the same state for each reference, buffer the input value and reference that buffer tag. For more information, see
Logix 5000
Controllers Common Procedures, publication 1756-PM001.You can also use Input and Output program parameters which automatically buffer the data during the
Logix Designer
application execution. See LOGIX 5000 Controllers Program Parameters Programming Manual, publication 1756-PM021.Provide Feedback