Declaration of global variables in ST

Syntax 
VAR_GLOBAL (* optional_begin *) {DMA := 'string'} CONSTANT RETAIN NON_RETAIN (* optional_end *)
  name_1, name_2, ..., name_n (* optional_begin *) {'key'} AT %address (* optional_end *) : data-type := initial-value;
  name_3, name_4, ..., name_n (* optional_begin *) {'key'} AT %address (* optional_end *) : STRING[length] := 'initial-value';
  name_5, name_6, ..., name_n (* optional_begin *) {'key'} AT %address (* optional_end *) : ARRAY [x..y] OF data-type := [initial-value_1, initial-value_2, .., initial-value_n];
  name_7, name_8, ..., name_n (* optional_begin *) {'key'} AT %address (* optional_end *) : ARRAY [x1..y1, x2..y2, x3..y3] OF data-type;  (* Here, initial values are possible as well. *)
 
(* Additional pieces of data, such as partial addresses, are also possible for the variables. *)  
(* Note: If a function block type is used as type for the variable, it is actually a function block instance. *)
END_VAR
Meaning  

declaration of one or more →global variables, name_1, name_2 etc. must be →IEC-identifiers.
The declaration of more sections of this kind is allowed.

Enhancement to IEC-standard

This is an enhancement to the →IEC-standard which allows only one such section for resource-global or configuration-global variables. Moreover, it is possible to declare global variables within a global-object and to insert here just a reference (observe that the syntax elements might differ).

The declaration of program-global variables is possible within an ST-object, in particular within the declaration of program. Access to such global variables is done in the context of other →POUs (FUNCTION, FUNCTION_BLOCK) – by using →external variables.

The declaration of resource-global variables or configuration-global variables is possible within a PLC-object, in particular within the declaration of a →resource or of a →configuration. Access to such global variables is done in the context of POUs (PROGRAM, FUNCTION, FUNCTION_BLOCK) – also by using external variables. See "Declaring global variables for resource or configuration and using them".

The optional attributes DMA (= Direct Memory Access) and key are intended for system integrators.

Providing the optional keyword CONSTANT prevents all global variables of this section from being overwritten during program execution (makes them →constants).
Providing the optional keyword RETAIN or NON_RETAIN  makes all variables of this section →retentive or non-retentive. If variables are declared based on a structured data type within the section with RETAIN or NON_RETAIN, its structure elements (incl. nestings) are treated as retentive or non-retentive alike. 

See "Supported data types" to learn which data types are supported for the declaration of variables. Use the optional →initial value [:= initial-value] to assign a value to the variable (see "Initialization of variables in ST" for details).
Moreover, it is possible to declare:

 

Use the optional keyword AT to assign a physical address in the →PLC to the symbolic variable. 

Examples for physical addresses:

Example

Explanation

%QB7

output, byte, 7th element (in the 1st level)

%IX1

input, bool, 1st element (in the 1st level)

%I1

input, bool, 1st element (in the 1st level)

%IW2.5.7.3

input, word, 3rd element in the 7th "module" in the 5th "rack" of the 2nd "bus"

If you are using EtherCAT fieldbuses that can be addressed via →EC-Master and →EC-Engineer, see "Accessing hardware IOs via EC-Master and EC-Engineer of Acontis" for information on access of their hardware IOs.

Necessary structure for physical address

Enter a physical address according to this structure:

 

Character

Meaning

1.

%

initiates the address

2.

prefix for location

defines the location

 

I

input

 

Q

output

 

M

memory

3.

prefix for size

defines the size

 

X or none

bool (single bit)

 

B

byte (8 bits)

 

W

word (16 bits)

 

D

double word (32 bits)

 

L

long word (64 bits)

4.

one or more →unsigned integers
You must separate the integers by . in order to enter hierarchical levels.
Enter the highest level as leftmost number, the lower levels as numbers to the right. 

Restriction

Depending on the PLC platform and the IO provider, Neuron Power Engineer supports max. 5 levels. Contact your system integrator for details.
The highest possible number per level is: 4_294_967_295 (that corresponds to UINT32_MAX) – The underscore characters _ are inserted as separators to make the value more readable, hence _ is not significant.

 

defines the address

 
Good to know

(grey lightbulb) Moreover, Neuron Power Engineer allows you to define a not yet fully specified location for the declaration. See "Declaration of a language element with partial address in ST" for details.

(grey lightbulb) Moreover, Neuron Power Engineer allows you to specify additional data for the declaration. See "Defining description, comment, JSON string or type for variables or data types" for details.

(grey lightbulb) Within a section VAR_GLOBAL...END_VAR, it is also possible to declare function block instances.
Example 
VAR_GLOBAL
  portSetting : INT;
  upTime : TIME;
  gVar1: ARRAY [1..2] of BOOL;
  gVar2 : STRING[10];
END_VAR

Example for assigning a physical address

 
VAR_GLOBAL
  VALVE_POS AT %QW28 : INT;
END_VAR