IEC_61131-3.pdf

12Contents1 Introduction.91.1 Subject of the Book.101.2 The IEC 61131 standard.121.2.1 Goals and benefits of the standard.12Manufacturers(PLC hardware and software).13Customers.131.2.2 History and components.141.3 The OrganisationPLCopen.161.3.1 Aims.161.3.2 Committees and fields of activity.171.3.3 Results.18Certification.18Exchange format for user programs.192 Building Blocks of IEC 61131-3.212.1 Introduction to the New Standard.212.1.1 Structure of the building blocks.22Declaration of variables.22Code part of a POU.232.1.2 Introductory example written in IL.252.1.3 PLC assignment.272.2 The Program Organisation Unit(POU).302.3 Elements of a POU.322.3.1 Example.332.3.2 Declaration part.34Types of variables in POUs.35Characteristics of the POU interface.36The formal parameters and return values of a POU.37External and internal access to POU variables.372.3.3 Code part.392.4 The Function Block.412.4.1 Instances of function blocks.41What is an“instance”?.41Instance means “structure”.43Instance means “memory”.452 ContentsRelationship between FB instances and data blocks.462.4.2 Re-usable and object-oriented FBs.472.4.3 Types of variables in FBs.482.5 The Function.482.5.1 Types of variables in functions and the function value.492.5.2 Execution control with EN and ENO.502.6 The Program.522.7 Calling Functions and Function Blocks.532.7.1 Mutual calls of POUs.532.7.2 Recursive calls are forbidden.542.7.3 Calling with formal parameters.562.7.4 Calls with input parameters omitted or in a different order.592.7.5 FB instances as actual FB parameters.60Example of an indirect FB call.62FB instance names as actual parameters of functions.63Function values as actual parameters.632.8 Summary of POU Features.643 Variables,Data Types and Common Elements.653.1 Simple Language Elements.653.1.1 Reserved keywords.673.2 Literals and Identifiers.683.2.1 Literals.683.2.2 Identifiers.703.3 Meanings of Data Types and Variables.713.3.1 From direct PLC addresses via symbols to variables.723.3.2 The data type determines the properties of variables.733.3.3 Type-specific use of variables.743.3.4 Automatic mapping of variables onto the PLC.753.4 Data Types.753.4.1 Elementary data types.763.4.2 Derived data types(type definition).77Additional properties for elementary data types.78Arrays.80Data structures.81Initial values in type definitions.833.4.3 Generic data types.843.5 Variables.853.5.1 Inputs,outputs and flags as special variables.863.5.2 Multi-element variables:arrays and structures.883.5.3 Assignment of initial values at the start of a program.903.5.4 Attributes of variable types.913.5.5 Graphical representation of variable declarations.93Contents 34 The New Programming Languages of IEC 61131-3.954.1 Instruction List IL.964.1.1 Instruction in IL.964.1.2 The universal accumulator(Current Result).974.1.3 Operators.100Negation of the operand.100Nesting levels by parenthesis.100Conditional execution of operators.1014.1.4 Using functions and function blocks.104Calling a function.104Calling a function block.1064.1.5 IL example:Mountain railway.1074.2 Structured Text ST.1114.2.1 ST statements.1114.2.2 Expression:Partial statement in ST.113Operands.113Operators.113Function as operator.1154.2.3 Statement:Assignment.1164.2.4 Statement:Call of function blocks.1184.2.5 Statement:RETURN.1184.2.6 Statement:Selection and Multi-selection.119Selection.119Multi-selection.1204.2.7 Statement:Iteration.122WHILE and REPEAT statements.122FOR statement.123EXIT statement.1254.2.8 Example:Stereo cassette recorder.1254.3 Function Block Diagram FBD.1284.3.1 Networks,graphical elements and connections of LD and FBD.128Network label.128Network comment.129Network graphic.1294.3.2 Network architecture in FBD.1314.3.3 Graphical objects in FBD.133Connections.134Execution control(jumps).134Call of functions and function blocks.1354.3.4 Programming methods in FBD.136Network evaluation.136Feedback variable.1374.3.5 Example:Stereo cassette recorder.137Comments on the networks of Example 4.24 and Example 4.31.1404 Contents4.4 Ladder Diagram LD.1414.4.1 Networks,graphical elements and connections(LD).1414.4.2 Network architecture in LD.1414.4.3 Graphical objects in LD.142Connections.142Contacts and coils.143Execution control.147Call of functions and function blocks.1484.4.4 Programming methods in LD.149Network evaluation.149Feedback variable.1514.4.5 Example in Ladder Diagram:Mountain railway.153Comments on the mountain railway networks.1564.5 The American way of Ladder programming.1594.5.1 Network Layout.1594.5.2 Module addresses and memory areas.1614.5.3 Configuration.1634.6 Sequential Function Chart SFC.1644.6.1 Step/Transition combination.1654.6.2 Step-transition sequence.1674.6.3 Detailed description of steps and transitions.172Step.172Transition.1744.6.4 Step execution using action blocks and actions.1794.6.5 Detailed description of actions and action blocks.181Actions.181Action block.1824.6.6 Relationship between step,transition,action and action block.1854.6.7 Act