Concept V2.5

Lesson 17 Objectives:After completing this lesson, the learner will be

able to:– Program logic using the ST Editor.– Demonstrate an Understanding of ST Language.

Concept V2.5

Overview

ST is a high level language, similar to PASCAL or BASIC.

ST is a distinct language that has been specifically developed for industrial control applications.

ST has a comprehensive range of constructs for assigning values to variables, calling FFBs, creating expressions, for conditional evaluation of selected statements, or for iteration, i.e. repeating selected section of code.

Concept V2.5

AdvantagesFairly straight forward and easy to learn and to use.

Compact formulation of a complex programming task.

Clear program construction by instruction blocks.

Powerful constructs for controlling the instruction flow.

Useful for complex mathematic solutions.

Simple solutions for difficult problems in FBD, LD or IL.

Concept V2.5

Executed operationsLogical, arithmetic, compare operations and

allocations.

Complex instructions and instruction groupsunconditioned / conditioned.

Declaration of functions and function blocks.

Execute functions and function blocksunconditioned / conditioned.

Concept V2.5

Invocation of Function Blocks

Each FFB instance must be invoked once

Multiple invocation (instantiation) is allowed

FFB-call: with a list of input parameters

Concept V2.5

Statements, Expressions and OperatorsA structured text program contains:

• statements.

A statement contains: • Expressions

• Keywords

An expression contains one or more: • Operators with Operands

Admissible Operands• Literals, all variables, elements of multi-element

variables, FFB outputs or direct addresses

Concept V2.5

Statements must close with semicolons (;) One line may contain several statements, separated by (;)

The following statements are available: VAR ... END_VAR Declaration of FFB's Function Block Calls Invoking of FFBs IF ... THEN ... END_IF Conditioned execution of statements ELSIF ... THEN Conditioned execution of statements,

if the preceded expression is notfulfilled (false).

ELSE ... Execution of statements, if expressionsof preceded statements are not fulfilled(false).

NOTE: ( ... means condition/expression)

Concept V2.5

CASE ... OF ... END_CASE A list of statements with given labels. Execution, if the label is true.

FOR ... TO ... BY ... DO ... END_FOR Repeated execution of statements up to a

given number. WHILE...DO...END_WHILE Repeated execution of

statements up to preceded condition = 0.

REPEAT ... UNTIL ... END_REPEAT Repeated execution of statements up to

succeeded condition = 0. EXIT To terminate repeat

statements (FOR, WHILE, REPEAT) before the end condition is true.

NOTE: ( ... means condition/expression)

Concept V2.5

Keywords That Can Not Be used TYPE...END_TYP VAR_INPUT...END_VAR VAR_OUTPUT...END_VAR VAR_IN_OUT...END_VAR VAR_EXTERNAL...END_VAR FUNCTION...END_FUNCTION FUNCTION_BLOCK...END_FUNCTION_BLOCK PROGRAM...END_PROGRAM STEP...END_STEP TRANSITION...END_TRANSITION ACTION...END_ACTION SEGMENT_SCHEDULER RETURN

Concept V2.5

Operators

Operators are generic, i.e. they automatically adjust to the data type of the operand.

The evaluation of an expression consists of applying the operators to the operands in the order defined by the rule of precedence of the operators.

The operator with the highest rule of precedence in an expression will be executed first.

Operators with the same precedence are executed from left to right, as described in the expression.

This order can be changed through bracketing.

Concept V2.5

( ) Expression Bracketing 1 (highest)

FUNCNAME ANY Function editing (call) 2

* * REAL, ANY_NUM Raising to a power 3

ANY_NUM Negation 4

NOT ANY_BIT Complement 4

* ANY_NUM or TIME Multiplication 5

/ ANY_NUM Division 5

MOD ANY_NUM Modulo 5

All operands also: Expression, literal, variable, direct address

Operator Operand Significance Precedence

Concept V2.5

+ ANY_NUM or TIME Addition 6

ANY_NUM or TIME Subtraction 6

< ANY_ELEM Less than 7

> ANY_ELEM Greater than 7

< = ANY_ELEM Less or equal 7

> = ANY_ELEM Greater or equal 7

= ANY_ELEM Equality 8

< > ANY_ELEM Inequality 8

&, AND ANY_BIT Logic AND 9

XOR ANY_BIT Logic exclusive OR 10

OR ANY_BIT Logic OR 11

All operands also: Expression, literal, variable, direct address

Operator Operand Significance precedence

Concept V2.5

Input Output Default Data Type Possible Data Types%IX, %QX BOOL BOOL%I %Q

%IB %QB BYTE BYTE

%IW %QW INT INT, UINT, WORD

%ID %QD REAL REAL, DINT,UDINT, TIME

Example: %IX1 means address 100001 (input bit 1) %QW1 means address 400001 (output word 1)

Concept V2.5

Keywords, Separators and Comments

When entering keywords, separators and comments, there is an immediate spell check

If a keyword, a separator or a comment is detected, it is identified with a color shading.

If unauthorized keywords (instructions or operators) are entered, this will be identified through color shading as well.

Spaces and tabs have no effect on syntax, they can be used anywhere.

Concept V2.5

The Objects Menu

Concept V2.5

Example: Entering a direct function call

No declaration is required!

Concept V2.5

Example: Entering a function block

IN, PT, Q, and ETare the labels of thepins on a TON timer

Concept V2.5

Handling, general

Create or open ST Section

Type or select statement, operator etc.: Objects...

Type or select operand: Edit Lookup variables

Type or select FFB: Objects Insert FFB or click on

Insert FFB see next slide

Concept V2.5

Insert FFBBrowse and select FFBDeclaration InvocationAssignment

Concept V2.5

Use Expand statement to complete e.g.,VAR ... END_VAR

Use Go to counterpart to find e.g.,second bracket ( )

Enter comments, consider Options, Preferences!

Syntax check: Project Analyze Section.

Any errors found are displayed in the message window.

Double click on the first line means:go to the line with the first error in ST.

Concept V2.5

Code generation together with the syntax check will be performed when the section is closed.

creates additional information forprocess diagnosis during code generation

Tests loops within ST (and IL) sections

generates a runtime optimized code

Concept V2.5 Before closing the ST section, go to

Project Code generation options

This area used for Upload function

Concept Programming in STST Example

Comment

FFB-Declaration

AND-Function with Allocation

FFB call with Allocation

AND-Function with Allocation

FFB call with Allocation

Watch Selected

Inspect Selected

Concept V2.5

Concept V2.5

Select variable with double click

Animation Selected mode or

Go to Online Watch Selected

Repeat for next variable

Remains open until it is closed or the animation is terminated

A dialog box can be opened for each section

Concept V2.5 Select variable with double click

go to menu Online Inspect Selected

set cursor to any position on section

click left mouse button

Set cursor into cyan field

depress right mouse button

select operation mode:

Move field to another position

Delete field or

Options... see next slide

Concept V2.5

Select operation mode options... Enter Minimum/Maximum Notice the color change

Yellow Magenta