Program content

mapp Services V5.16

Structured Text programs

Structured Text programs are programmed in text files with extension ".st" or ".iec" as well as data objects with postfix "_st" or "_iec".

Structured Text programs are defined in section PROGRAM with attribute _MAIN. Attributes _INIT, _CYCLIC and _EXIT as used in Automation Studio ST are not supported.

In addition to program section _MAIN, the program can contain declaration sections.

Typical Structured Text program content

TYPE
  // Type declarations
END_TYPE
VAR
  // Variable declarations
END_VAR
PROGRAM _MAIN
  // Main program section
END_PROGRAM

ST program example

A Structured Text program with variable (constant) declaration and main program

VAR CONSTANT
P1 : PointType := (Pos:=(X:=100));
END_VAR
PROGRAM _MAIN
MoveLR(P1); // linear rapid movement
END_PROGRAM

Declaration files

In addition to Structured Text programs, the declaration sections can be defined in standalone declaration files.

Extension/Postfix	Recommended content
.var / _var	Variable declarations
.typ / _typ	Type declarations
.fun / _fun	Function / Function block declarations

Scope and storage

Scope defines the visibility of the element (variable, type, function, action) in ST programs.

The storage location defines the owner (location) of the element.

Scope and storage categories: Variable shared across all interpreter instances, e.g. all axis groups

•NC_GLOBAL: Element that is shared across all interpreter instances, e.g. all axis groups

•IP_GLOBAL: Element that is shared within the same interpreter instance, e.g. within the same axis group

•LOCAL: Element visible/shared within the file

The default scope is always defined by the file extension. Storage is always the same as scope. Storage for variables can be overridden in their declarations, however.

Extension/Postfix	Default scope
.st / _st	LOCAL
.iec / _iec	LOCAL
.var / _var	IP_GLOBAL
.typ / _typ	IP_GLOBAL
.fun / _fun	IP_GLOBAL

Examples

Comparison between variables declared in ST files and variables declared in VAR files

The file extension defines the default scope:

•In an ST file, the variable is only visible in the current program file.

•In a VAR file, the variable is visible in all files (program and declaration files).

Shared variables visible only in selected programs

Process variable "Home" (already created on the PLC) can be made available for all ST programs by declaring it in VAR file "defs.var". File "defs.var" must be loaded (started) before starting "program1.st" and "program2.st". The declaration of variable "Home" does not need to be repeated in ST programs "program1.st" and "program2.st".

Files "program1.st" and "program2.st" contain a declaration of variable "P1". This is due to file extension ".st", which is local to those files.

defs.var:

VAR {AT PLC}

Home : McPointType;

END_VAR

program1.st:

VAR CONSTANT

P1 : McPointType := (Pos:=(X:=100));

END_VAR

PROGRAM _MAIN

MoveJR(Home); //Rapid point-to-point movement

Feedrate(1000);