[水一篇] Structured Text(ST)

Structured Text (ST), a programming language used in
Programmable Logic Controllers (PLCs).

Structured Text is a high-level language that's widely used in industrial
automation and control systems. It's a text-based language that allows
programmers to write logic and control code for PLCs, which are used in
various industries such as manufacturing, oil and gas, water treatment,
and more.

ST is known for its ease of use, flexibility, and readability, making it a
popular choice among PLC programmers.

What is Structured Text (ST)?

Structured Text (ST) is a high-level programming language used to program
Programmable Logic Controllers (PLCs). It's a text-based language that
allows you to write logic and control code for PLCs.

Key Features of ST:

  1. Easy to Read: ST code is written in plain English, making it easy
    to understand and maintain.
  2. High-Level Language: ST is a high-level language, meaning it
    abstracts away from the low-level details of the hardware, allowing you to
    focus on the logic of your program.
  3. Platform Independent: ST code can be run on any PLC that supports
    the language, regardless of the manufacturer or model.

Basic Syntax:

Here's a simple example of an ST program:

PROGRAM Example
VAR
  Input : BOOL;
END_VAR

IF Input THEN
  Output := TRUE;
ELSE
  Output := FALSE;
END_IF

Let me explain what each part does:

  • PROGRAM is the keyword that starts a new program.
  • Example is the name of our program.
  • VAR declares variables, which are stored values used in our program.
    In this case, we have two variables: Input and Output.
  • The IF statement checks a condition (in this case, whether Input is
    TRUE or FALSE).
  • If the condition is true, then the code inside the THEN block is
    executed.
  • If the condition is false, then the code inside the ELSE block is
    executed.

Basic Data Types:

ST uses various data types to store values. Here are some common ones:

  1. BOOL: A boolean value that can be TRUE or FALSE.
  2. WORD: A 16-bit unsigned integer value.
  3. DWORD: A 32-bit unsigned integer value.
  4. REAL: A floating-point number with a maximum of 8 decimal places.

Control Statements:

ST supports various control statements, such as:

  1. IF-THEN-ELSE: Used to execute different code based on conditions.
  2. FOR: Used for looping through a range of values.
  3. WHILE: Used for looping until a condition is met.
  4. CASE: Used for executing different code based on the value of an
    expression.

That's a basic introduction to Structured Text (ST) and its syntax! Do you
have any specific questions or topics you'd like me to cover next?

teach me more
Let's dive deeper into Structured Text (ST) programming.

Variables and Data Types

In ST, variables are declared using the VAR keyword. Here are some
examples:

VAR
  Input : BOOL;  // boolean variable
  Counter : WORD := 0;  // 16-bit unsigned integer variable with initial 
value 0
  Temperature : REAL := 20.5;  // floating-point number variable with 
initial value 20.5
END_VAR

ST supports various data types, including:

  1. BOOL: A boolean value that can be TRUE or FALSE.
  2. WORD: A 16-bit unsigned integer value (0-65535).
  3. DWORD: A 32-bit unsigned integer value (0-4294967295).
  4. REAL: A floating-point number with a maximum of 8 decimal places
    (-3.40E38 to 3.40E38).
  5. TIME: A time value in hours, minutes, and seconds.

Operators

ST supports various operators for performing arithmetic, comparison,
logical, and assignment operations:

  1. Arithmetic Operators:
    • + (addition)
    • - (subtraction)
    • * (multiplication)
    • / (division)
    • MOD (modulo operation)
  2. Comparison Operators:
    • = (equal to)
    • <> (not equal to)
    • < (less than)
    • > (greater than)
    • <= (less than or equal to)
    • >= (greater than or equal to)
  3. Logical Operators:
    • AND (logical AND)
    • OR (logical OR)
    • NOT (logical NOT)

Control Statements

ST supports various control statements for executing different code:

  1. IF-THEN-ELSE:
IF Input THEN
  Output := TRUE;
ELSE
  Output := FALSE;
END_IF
  1. FOR:
FOR Counter := 0 TO 10 DO
  LED := TRUE;
END_FOR
  1. WHILE:
VAR
  Counter : WORD := 0;
END_VAR

WHILE Counter < 5 DO
  LED := TRUE;
  Counter := Counter + 1;
END_WHILE
  1. CASE:
CASE Input OF
  FALSE:
    Output := FALSE;
  TRUE:
    Output := TRUE;
END_CASE

Functions
ST supports user-defined functions for reusing code:

FUNCTION Add(a : WORD; b : WORD) : WORD
VAR
  Result : WORD;
END_VAR

Result := a + b;
RETURN Result;
END_FUNCTION

You can call the Add function using:

Output := Add(10, 20);

Arrays and Structures

ST supports arrays and structures for storing multiple values:

  1. Arrays:
VAR
  Array : ARRAY[0..9] OF WORD;
END_VAR

Array[5] := 50;
  1. Structures:
TYPE
  Point : STRUCT
    X : WORD;
    Y : WORD;
  END_STRUCT
END_TYPE

Point.X := 10;
Point.Y := 20;

These are some of the basic features and constructs in Structured Text
(ST). Do you have any specific questions or topics you'd like me to cover
next?

Loops

ST supports various types of loops for executing code repeatedly:

  1. FOR Loops:
FOR i := 0 TO 9 DO
  Output[i] := TRUE;
END_FOR
  1. WHILE Loops:
VAR
  i : WORD := 0;
END_VAR

WHILE i < 10 DO
  Output[i] := TRUE;
  i := i + 1;
END_WHILE
  1. DO-UNTIL Loops:
VAR
  i : WORD := 0;
END_VAR

DO
  Output[i] := TRUE;
  i := i + 1;
UNTIL i >= 10

Arrays

ST supports arrays for storing multiple values:

TYPE
  MyArray : ARRAY[0..9] OF WORD;
END_TYPE

You can initialize an array using:

MyArray := [0, 20, 30, 40, 50, 60, 70, 80, 90, 100];

Or you can access individual elements of the array using:

Output := MyArray[5];  // Output will be 50

Structures

ST supports structures for storing multiple values:

TYPE
  Point : STRUCT
    X : WORD;
    Y : WORD;
  END_STRUCT
END_TYPE

MyPoint : POINT;

You can initialize a structure using:

MyPoint := [X:=10, Y:=20];

Or you can access individual elements of the structure using:

Output := MyPoint.X;  // Output will be 10

Records

ST supports records for storing multiple values:

TYPE
  Point : RECORD
    X : WORD;
    Y : WORD;
  END_RECORD
END_TYPE

MyPoint : POINT;

You can initialize a record using:

MyPoint := [X:=10, Y:=20];

Or you can access individual elements of the record using:

Output := MyPoint.X;  // Output will be 10

Functions

ST supports user-defined functions for reusing code:

FUNCTION Add(a : WORD; b : WORD) : WORD
VAR
  Result : WORD;
END_VAR

Result := a + b;
RETURN Result;
END_FUNCTION

You can call the Add function using:

Output := Add(10, 20);  // Output will be 30

Subroutines

ST supports subroutines for executing code:

SUBROUTINE MySub
VAR
  i : WORD;
END_VAR

FOR i := 0 TO 9 DO
  Output[i] := TRUE;
END_FOR
END_SUBROUTINE

You can call the MySub subroutine using:

MySub();

Type Definitions

ST supports type definitions for creating new data types:

TYPE
  MyType : TYPE DEFINITION OF WORD;
END_TYPE

You can use the MyType type in your code like any other built-in type.

Library Functions

ST supports library functions for accessing pre-defined functions and
variables:

VAR
  i : WORD := Lib_Add(10, 20);
END_VAR

You can use library functions to access pre-defined functions and
variables.
Object-Oriented Programming

ST supports object-oriented programming (OOP) concepts such as classes,
objects, inheritance, and polymorphism:

  1. Classes:
CLASS MyClass
VAR
  X : WORD;
END_VAR

CONSTRUCTOR MyClass
VAR
  i : WORD := 0;
END_VAR

X := i;
END_CONSTRUCTOR
  1. Objects:
VAR
  myObject : MyClass;
END_VAR

myObject := new();
  1. Inheritance:
CLASS MySubClass : MyClass
VAR
  Y : WORD;
END_VAR

CONSTRUCTOR MySubClass
VAR
  i : WORD := 0;
END_VAR

Y := i;
END_CONSTRUCTOR
  1. Polymorphism:
FUNCTION MyFunction(obj : OBJECT)
VAR
  result : WORD;
END_VAR

CASE obj OF
  MyClass :
    result := MySubClass.X;
  MySubClass :
    result := MySubClass.Y;
END_CASE

RETURN result;
END_FUNCTION

Event-Driven Programming

ST supports event-driven programming (EDP) concepts such as events,
handlers, and publishers:

  1. Events:
EVENT MyEvent
VAR
  data : WORD;
END_VAR
  1. Handlers:
ON_EVENT(MyEvent)
VAR
  i : WORD := 0;
END_VAR

data := i;
END_ON_EVENT
  1. Publishers:
PUBLISH(MyEvent, 10);

Graphical User Interface

ST supports graphical user interface (GUI) programming concepts such as
windows, buttons, labels, and text boxes:

  1. Windows:
WINDOW MyWindow
VAR
  width : WORD := 400;
END_VAR

CREATE(MyWindow, width, 300);
  1. Buttons:
BUTTON MyButton
VAR
  text : STRING := "Click me!";
END_VAR

CREATE(MyButton, 100, 50);
  1. Labels:
LABEL MyLabel
VAR
  text : STRING := "Hello, world!";
END_VAR

CREATE(MyLabel, 150, 20);
  1. Text boxes:
TEXT_BOX MyTextBox
VAR
  width : WORD := 200;
END_VAR

CREATE(MyTextBox, width, 50);

**Networking^[[200~```st
TYPE
Point : RECORD
X : WORD;
Y : WORD;
END_RECORD
END_TYPE

MyPoint : POINT;

You can initialize a record using:
```st
MyPoint := [X:=10, Y:=20];

Or you can access individual elements of the record using:

Output := MyPoint.X;  // Output will be 10

Functions

ST supports user-defined functions for reusing code:
^[[201~**

ST supports networking programming concepts such as sockets, clients, and
servers:

  1. Sockets:
SOCKET MySocket
VAR
  port : WORD := 8080;
END_VAR

CREATE(MySocket, port);
  1. Clients:
CLIENT MyClient
VAR
  server : STRING := "localhost";
END_VAR

CONNECT(MyClient, server, 8080);
  1. Servers:
SERVER MyServer
VAR
  port : WORD := 8080;
END_VAR

LISTEN(MyServer, port);

Database

ST supports database programming concepts such as connections, queries,
and transactions:

  1. Connections:
DATABASE MyDatabase
VAR
  host : STRING := "localhost";
END_VAR

CONNECT(MyDatabase, host);
  1. Queries:
QUERY MyQuery
VAR
  query : STRING := "SELECT * FROM users;";
END_VAR

EXECUTE(MyQuery, query);
  1. Transactions:
TRANSACTION MyTransaction
VAR
  transaction : BOOL := TRUE;
END_VAR
BEGIN(MyTransaction);
...
COMMIT(MyTransaction);

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posted @ 2024-10-30 21:57  科里布  阅读(12)  评论(0)  编辑  收藏  举报