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3.1.2
Symbolic Variables
Symbolic variables are variables for which you do not specify a reference address (similar to a
variable in a typical high-level language). Except as noted in this section, you can use these in the
same ways that you use mapped variables.
In the programming software, a symbolic variable is displayed with a blank address. You can change
a mapped variable to a symbolic variable by removing the reference address from the variable's
properties. Similarly, you can change a symbolic variable into a mapped variable by specifying a
reference address for the variable in its properties.
The memory required to support symbolic variables counts against user space. The amount of space
reserved for these variables is configured on the Memory tab in the CPU hardware configuration.
Restrictions on the Use of Symbolic Variables
▪
Symbolic variables cannot be used with indirect references (for example, @Name). For a full
description, refer to Indirect References.
Only global scope Symbolic variables can be used in EGD pages.
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A variable must be globally scoped and published (internal or external) to be used in a C block.
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Symbolic variables cannot be used in the COMMREQ status word.
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Use of symbolic variables is not supported on web pages.
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Symbolic Boolean variables are not allowed on non-BOOL parameters.
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Symbolic non-discrete variables cannot be used on Series 90-70 style Transition contacts and
coils. (Symbolic discrete variables are supported.)
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Overrides and Forces cannot be used on symbolic non-discrete variables. (Symbolic discrete
variables are supported.)
▪
Arrays of the following data types are not supported:
o Arrays of user defined function block (UDFB) instance variables.
o Arrays of PACMotion function block instance variables.
o Arrays of TON, TOF, or TP instance variables.
o Arrays of reference ID variables (RIVs) that contain one or more linked RIV elements.
Note: An RIV array is supported when none of its elements is linked.
GFK-2950C
February 2018
Chapter 3. Program Data
31
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