A data type alias is the declaration of a user-defined data type with which an alternative name for a basic type, data type, or function block is generated.
You make the type declaration of an alias in a “DUT” object which you create in the “Project Add Object DUT” menu or in the context menu of an application.
Syntax:
TYPE <DUT name> : <type name>; END_TYPE
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Example
Alias data type for variables of type STRING or ARRAY if they require a specific length
Declaration
TYPE FRAME : ARRAY[0..1499] OF BYTE; END_TYPE TYPE SYMBOL : STRING(512); END_TYPE
Call
PROGRAM PLC_PRG VAR frameF : FRAME; symbolS : SYMBOL; END_VAR
Example
Alias data type for variables which require a different initial value than the one provided by the compiler
TYPE INDEX : DINT := -1; END_TYPE
Example
Alias data type for variables of a specific type which should apply only a specific subset of values of the original type
{attribute 'qualified_only'}
VAR_GLOBAL CONSTANT
c_diMaxRune : DINT := DINT#16#0010FFFF;
END_VAR
TYPE RUNE : DINT(0..GVL.c_diMaxRune); END_TYPE
Example
Alias data type for types from another namespace
For example, for types from a subordinate library which should be available in the current namespace.
TYPE ENCODING: SBB.ENCODING; END_TYPE (*ENUM*) TYPE RUNE : UTF8.RUNE; END_TYPE (*SUBTYPE*) TYPE INFO : STR.IFNFO; END_TYPE (*STRUCT*) TYPE IBuilder : SBB.IBuilder; END_TYPE (*INTERFACE*) TYPE Tange: SBB.Range; END_TYPE (*FUNCTION_BLOCK*)