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Structured Text
Structured text, abbreviated as ST or STX, is one of the five languages supported by the IEC 61131-3 standard, designed for programmable logic controllers (PLCs). It is a high level language that is block structured and syntactically resembles Pascal, on which it is based. All of the languages share IEC61131 Common Elements IEC 61131-3 is the third part (of 10) of the open international standard IEC 61131 for programmable logic controllers. It was first published in December 1993 by the IEC; the current (third) edition was published in February 2013. Part 3 of ''IEC .... The variables and function calls are defined by the common elements so different languages within the IEC 61131-3 standard can be used in the same program. Complex statements and nested instructions are supported: * Iteration loops (REPEAT-UNTIL; WHILE-DO) * Conditional execution (IF-THEN-ELSE; CASE) * Functions (SQRT(), SIN()) Sample program (* simple state machine *) TxtState := STATES tateMachine CAS ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IEC 61131-3
IEC 61131-3 is the third part (of 10) of the open international standard IEC 61131 for programmable logic controllers. It was first published in December 1993 by the IEC; the current (third) edition was published in February 2013. Part 3 of ''IEC 61131'' deals with basic software architecture and programming languages of the control program within PLC. It defines three graphical and two textual programming language standards: * Ladder diagram (LD), graphical * Function block diagram (FBD), graphical * Structured text (ST), textual * Instruction list (IL), textual (deprecated in 3rd edition of the standard) * Sequential function chart (SFC), has elements to organize programs for sequential and parallel control processing, graphical. Data types * Elementary Data Type ** Bit Strings – groups of on/off values *** BOOL - 1 bit (0,1) *** BYTE – 8 bit (1 byte) *** WORD – 16 bit (2 byte) *** DWORD – 32 bit (4 byte) *** LWORD – 64 bit (8 byte) ** INTEGER – whole numbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Programmable Logic Controller
A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis. Dick Morley is considered as the father of PLC as he had invented the first PLC, the Modicon 084, for General Motors in 1968. PLCs can range from small modular devices with tens of inputs and outputs (I/O), in a housing integral with the processor, to large rack-mounted modular devices with thousands of I/O, and which are often networked to other PLC and SCADA systems. They can be designed for many arrangements of digital and analog I/O, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory. PLCs were first devel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block (programming)
In computer programming, a block or code block or block of code is a lexical structure of source code which is grouped together. Blocks consist of one or more Declaration (computer programming), declarations and Statement (computer science), statements. A programming language that permits the creation of blocks, including blocks Nesting (computing), nested within other blocks, is called a block-structured programming language. Blocks are fundamental to structured programming, where control structures are formed from blocks. Blocks have two functions: to group statements so that they can be treated as one statement, and to define scope (computer science), scopes for name binding, names to distinguish them from the same name used elsewhere. In a block-structured programming language, the objects named in outer blocks are visible inside inner blocks, unless they are Name masking, masked by an Object (computer science), object declared with the same name. History Ideas of block st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pascal (programming Language)
Pascal is an imperative and procedural programming language, designed by Niklaus Wirth as a small, efficient language intended to encourage good programming practices using structured programming and data structuring. It is named in honour of the French mathematician, philosopher and physicist Blaise Pascal. Pascal was developed on the pattern of the ALGOL 60 language. Wirth was involved in the process to improve the language as part of the ALGOL X efforts and proposed a version named ALGOL W. This was not accepted, and the ALGOL X process bogged down. In 1968, Wirth decided to abandon the ALGOL X process and further improve ALGOL W, releasing this as Pascal in 1970. On top of ALGOL's scalars and arrays, Pascal enables defining complex datatypes and building dynamic and recursive data structures such as lists, trees and graphs. Pascal has strong typing on all objects, which means that one type of data cannot be converted to or interpreted as another without explicit conversi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IEC61131 Common Elements
IEC 61131-3 is the third part (of 10) of the open international standard IEC 61131 for programmable logic controllers. It was first published in December 1993 by the IEC; the current (third) edition was published in February 2013. Part 3 of ''IEC 61131'' deals with basic software architecture and programming languages of the control program within PLC. It defines three graphical and two textual programming language standards: * Ladder diagram (LD), graphical * Function block diagram (FBD), graphical * Structured text (ST), textual * Instruction list (IL), textual (deprecated in 3rd edition of the standard) * Sequential function chart (SFC), has elements to organize programs for sequential and parallel control processing, graphical. Data types * Elementary Data Type ** Bit Strings – groups of on/off values *** BOOL - 1 bit (0,1) *** BYTE – 8 bit (1 byte) *** WORD – 16 bit (2 byte) *** DWORD – 32 bit (4 byte) *** LWORD – 64 bit (8 byte) ** INTEGER – whole numbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Switch Statement
In computer programming languages, a switch statement is a type of selection control mechanism used to allow the value of a variable or expression to change the control flow of program execution via search and map. Switch statements function somewhat similarly to the if statement used in programming languages like C/C++, C#, Visual Basic .NET, Java and exists in most high-level imperative programming languages such as Pascal, Ada, C/C++, C#, Visual Basic .NET, Java, and in many other types of language, using such keywords as switch, case, select or inspect. Switch statements come in two main variants: a structured switch, as in Pascal, which takes exactly one branch, and an unstructured switch, as in C, which functions as a type of goto. The main reasons for using a switch include improving clarity, by reducing otherwise repetitive coding, and (if the heuristics permit) also offering the potential for faster execution through easier compiler optimization in many cases. His ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IEC Standards
This is an incomplete list of standards published by the International Electrotechnical Commission (IEC). The numbers of older IEC standards were converted in 1997 by adding 60000; for example IEC 27 became IEC 60027. IEC standards often have multiple sub-part documents; only the main title for the standard is listed here. * IEC 60027 Letter symbols to be used in electrical technology * IEC 60028 International standard of resistance for copper * IEC 60034 Rotating electrical machines * IEC 60038 IEC Standard Voltages * IEC 60041 Field acceptance tests to determine the hydraulic performance of hydraulic turbines, storage pumps and pump-turbines * IEC 60044 Instrument transformers * IEC 60045 Steam turbines * IEC 60050 International Electrotechnical Vocabulary * IEC 60051 Direct acting indicating analogue electrical measuring instruments and their accessories * IEC 60052 Voltage measurement by means of standard air gaps * IEC 60055 Paper-insulated metal-sheathed cables for rated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Programmable Logic Controllers
A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis. Dick Morley is considered as the father of PLC as he had invented the first PLC, the Modicon 084, for General Motors in 1968. PLCs can range from small modular devices with tens of inputs and outputs (I/O), in a housing integral with the processor, to large rack-mounted modular devices with thousands of I/O, and which are often networked to other PLC and SCADA systems. They can be designed for many arrangements of digital and analog I/O, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory. PLCs were first de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
