Declaration of in-out variables in ST
VAR_IN_OUT name_1, name_2, ..., name_n : data-type; name_3, name_4, ..., name_n : STRING[length]; name_5, name_6, ..., name_n : ARRAY [x..y] OF type; name_7, name_8, ..., name_n : ARRAY [x1..y1, x2..y2, x3..y3] OF type;(* Additional pieces of data are also possible for the variables. *)END_VAR|
Bedeutung |
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Declaration of one or more →in-out variables, name_1 , name_2 etc. must be →IEC-identifiers. A →data type is possible as a type for a variable. See "Supported data types" to learn which data types are supported for the declaration of variables. Moreover, it is possible to declare:
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Moreover, logi.CAD 3
allows you to specify additional data for the declaration
. See "
Defining description, comment, JSON string or type for variables or data types
" for details.
Within a section VAR_IN_OUT...END_VAR, it is also possible to declare function block instances.
VAR_IN_OUT In_out1 : INT; In_out2: ARRAY [1..2] of BOOL; In_out3 : STRING[10]; END_VARMind the following when you are using in-out variables:
→Assignments to in-out variables demand expressions on the right side of the assignment operator ":=" which might be on the left side of the assignment operator ":=" as well. Moreover, in case of a variable, it must be a non-temporary variable (compare: →temporary variable).
For calls of blocks with in-out variables, you have to use formal calls (see FAQ article " When to use a formal call? When to use a non-formal call?" for information when to use formal calls). Moreover, the in-out variables must always be of the same data type because a n implicit conversion for in-out variables is not allowed. It is not allowed to assign an in-out variable to itself within the call – thus, this call is not possible: MyFB(In_out1 := MyFB.In_out1);
The call of a function block instance is allowed, when it has been declared as in-out variable.
The reading access to an in-out variable is not allowed outside of the function block or the function. Likewise, an assignment to it outside the call of the function block or the function is not allowed.
In case of calling a function block instance it is possible to assign an →input variable to an in-out variable of the same function block instance. However, logi.cals advises you not to do so because subsequently it would be possible to modify values for input variables within the function block. This is not allowed according to the →IEC-standard.