IEC 61131-3 - AbsoluteAstronomy.com

IEC 61131-3 is the third part (of 8) of the open international standard

International standard

International standards are standards developed by international standards organizations. International standards are available for consideration and use, worldwide...

IEC 61131

IEC 61131 is an IEC standard for Programmable logic controllers . It was known as IEC 1131 before the change in numbering system by IEC.-Sections of IEC 61131:Standard IEC 61131 is divided into several parts :* Part 1: General information...

for programmable logic controller

Programmable logic controller

A programmable logic controller or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines...

s, and was first published in December 1993 by the IEC

International Electrotechnical Commission

The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...

. The current (second) edition was published in 2003.

Part 3 of IEC 61131 deals with programming languages and defines two graphical and two textual PLC

Programmable logic controller

programming language standards:

Ladder diagram
Ladder logic
Ladder logic is a programming language that represents a program by a graphical diagram based on the circuit diagrams of relay logic hardware. It is primarily used to develop software for programmable logic controllers used in industrial control applications...

(LD), graphical
Function block diagram
Function block diagram
A function block diagram is a block diagram that describes a function between input variables and output variables. A function is described as a set of elementary blocks. Input and output variables are connected to blocks by connection lines...

(FBD), graphical
Structured text
Structured text
Structured text is one of the 5 languages supported by the IEC 61131-3 standard. It is designed for programmable logic controllers . It is a high level language that is block structured and syntactically resembles Pascal. All of the languages share IEC61131 Common Elements...

(ST), textual
Instruction list
Instruction list
Instruction List is one of the 5 languages supported by the IEC 61131-3 standard. It is designed for programmable logic controllers . It is a low level language and resembles assembly. All of the languages share IEC61131 Common Elements...

(IL), textual
Sequential function chart
Sequential function chart
Sequential function chart is a graphical programming language used for PLCs. It is one of the five languages defined by IEC 61131-3 standard...

(SFC), has elements to organize programs for sequential and parallel control processing
Parallel computing
Parallel computing is a form of computation in which many calculations are carried out simultaneously, operating on the principle that large problems can often be divided into smaller ones, which are then solved concurrently . There are several different forms of parallel computing: bit-level,...

.

Data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...

Types

Bit Strings - groups of on/off values
- BOOL
  Boolean datatype
  In computer science, the Boolean or logical data type is a data type, having two values , intended to represent the truth values of logic and Boolean algebra...
  
  - 1 bit
- BYTE
  Byte
  The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...
  
  - 8 bit
- WORD - 16 bit
- DWORD - 32 bit
- LWORD - 64 bit

INTEGER
Integer (computer science)
In computer science, an integer is a datum of integral data type, a data type which represents some finite subset of the mathematical integers. Integral data types may be of different sizes and may or may not be allowed to contain negative values....

- whole numbers
- SINT - signed short (1 byte)
- INT - signed integer (2 byte)
- DINT - double integer (4 byte)
- LINT - long integer (8 byte)
- U - Unsigned - prepend a U to the type to make it unsigned integer.

REAL
Real number
In mathematics, a real number is a value that represents a quantity along a continuum, such as -5 , 4/3 , 8.6 , √2 and π...

- floating point IEC 559 (IEEE)
- REAL - (4 byte)
- LREAL - (8 byte)

TIME - duration for timers, processes.

Date and Time of day:
- DATE - calendar date
- TIME_OF_DAY - clock time
- DATE_AND_TIME: time and date

STRING
String (computer science)
In formal languages, which are used in mathematical logic and theoretical computer science, a string is a finite sequence of symbols that are chosen from a set or alphabet....

- character strings surrounded by single quotes.
Escaped characters are preceded by a dollar sign.
($$ $' $L $N $P $R $T $xx) => ($ quote linefeed newline page(FF) return tab hex_value)
- WSTRING - holds multi-byte strings
  String (computer science)
  In formal languages, which are used in mathematical logic and theoretical computer science, a string is a finite sequence of symbols that are chosen from a set or alphabet....
  
  .

Arrays - multiple values stored in the same variable
Variable (programming)
In computer programming, a variable is a symbolic name given to some known or unknown quantity or information, for the purpose of allowing the name to be used independently of the information it represents...

.

Sub Ranges - puts limits on value i.e., (4-20) for current

Derived - type derived from one of the above types.
- TYPE - single type
- STRUCT - composite of several variables and types.

Generic - groups of the above types:
- ANY
  - ANY_DERIVED
  - ANY_ELEMENTARY
  - ANY_MAGNITUDE
    - ANY_NUM - LREAL, REAL
    - ANY_INT - LINT, DINT, INT, SINT, ULINT, UDINT, UINT, USINT
  - ANY_BIT - LWORD, DWORD, WORD, BYTE, BOOL
  - ANY_STRING - STRING, WSTRING
  - ANY_DATE - DATE, TOD, DT

Variables

Variable attributes: RETAIN, CONSTANT, AT

Global
Direct (local)
I/O
I/O
I/O may refer to:* Input/output, a system of communication for information processing systems* Input-output model, an economic model of flow prediction between sectors...

Mapping - Input, Output, I/O
External
Temporary

Configuration

Resource - Like a CPU
Tasks - Can be multiple per CPU.
Programs
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

- Can be executed once, on a timer, on an event.

Program Organization Units

Functions
- Standard: ADD, SQRT, SIN, COS, GT, MIN, MAX, AND, OR, etc.
- Custom
Function Blocks
- Standard:
- Custom - Libraries of functions can be supplied by a vendor or third party.
Programs

Configuration, Resources, Tasks

Configuration - processing resources, memory for IO, execution rates, number of tasks.

External Links

Beginners PLC Primer

Forums on LinkedIn

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