KE Process Automation project work - ABB 800xA PLC programming

Transcription

1 KE Process Automation project work - ABB 800xA PLC programming (This material is built using ABB T314 course materials, T314-6 Variables and Data types, T FBD, T ST, T CM & T SFC.) Contents 1 Data Types Variable data types Simple Data Types Structured Data Types System defined I/O Data Types Global variables Local variables Function Block Diagram FBD Editor Execution Rules Functions in FBD FBD Pane Toolbar Buttons Inserting a Function / Function Block EN Input Parameter Editing Parameter Properties Making Connections Inverting Connections Adding Comments Structure Pane Structured Text (ST) Structured Text Editor Basic Language Elements Assignment Statements Comment Statements Operators Precedence

2 3.2.5 Conditional Structures Iteration Structures RETURN Statement Functions and Function Blocks Functions Function Blocks How to Declare Function Block Instances How to Call a Function Block Instance Common Mistakes and their Error Messages Identifier, constant or opening parenthesis expected Variable name is not unique Identifier too long or invalid Undefined function block Type mismatch in assignment Incompatible types in expression Sequential Function Charts (SFC) SFC Editor Steps and Transitions Steps Transition Sequence Constructs Simultaneous Sequences Sequence Selection Jumps and Destinations Control Modules Control Modules as Code Containers Code Graphics Representation of Control Modules When to use what? Control Module Diagram (CMD) Editor How to Create a Control Module Instance Graphical Connections

3 1 Data Types Variables are used to store data inside the controller memory. During execution of the control code the data may change following changes in the process states or else due to calculations made. When the application code is written, the programmer must create variables to store the data which is manipulated by the application code. Variables are the containers for values within the application, its programs, its function blocks and its control modules. Modern controllers are capable of handling many different sorts of data. The simplest type is boolean, but other types are possible such as integer (whole numbers), real (floating point numbers) and string (character strings such as text messages). Additionally, in System 800xA, many other more complex data types are possible. Variables are declared in an application by opening the application editor from the Project Explorer tree: 1.1 Variable data types The following rules apply when declaring a variable: A variable name may have up to 32 characters The name of the variable must not begin with a number No spaces are permitted in a variable name In general use only alphanumeric characters and the underscore character. Do not include any special characters such as $, # or others. Variable names are NOT case sensitive. A variable may not have a Key word as a name. Some key words are reserved by the system and you will be warned if you have used a key word for a variable name. Within any one POU (application, control module, function block or program), variable names must be unique Simple Data Types Bool (True/False), Dint(± ), Uint ( ), String[length(40)], Dword (32bits), Word (16bits), Time, Date_And_Time, Real (±1,7014*10^±38) Structured Data Types Structured data types have two or more components. The components may be simple or themselves structured. They can also be seen as wires in a multicore cable or a basket. 3

4 For example, suppose you have a vessel which has the following data associated with it: Tank is Full The volume of fluid (measured in cubic meters). The temperature of the fluid (measured in Kelvin). The minimum permitted temperature of the fluid. The maximum permitted temperature of the fluid (both measured in Kelvin). This data could be packed into a data type called say, TankType. Once the TankType data type has been defined, variables of that type may be declared in any application. Suppose a variable is now declared called Tank1. The individual componets of this variable may be accessed using dot notation : Tank1.Full, Tank1.Volume, Tank1.Temperature, Tank1.MinTemp, Tank1.MaxTemp System defined I/O Data Types Although it is allowed to connect simple variables of type Bool and Real to digital and analogue I/O channels respectively, it is better to use the system defined I/O data types called BoolIO and RealIO. DintIO is used to connect to integer channels on, for example, a pulse counter module. DwordIO may be used to access all 16 channels on a DI or DO module as a word rather than as individual IO points BoolIO Use a BoolIO type when you connect to either a digital input or digital output channel. The datatype is defined by the system and has the following components: Name Data Type Description Value Bool Value used by the application code IOValue Bool Value of the I/O channel. IOValue and Value are equal if the channel is not forced Forced Bool Indicates whether or not the channel is forced. Status Dword Status as a hexadecimal integer RealIO Use a RealIO type when you connect to an analog input or analog output channel. The Value, IOValue, Forced and Status components are given by the system to the application. The Inverted, Max, Min, Unit and Fraction components are given by the user of the application to the system in the Scaling tab. The data type has the following components. 4

5 Name Data Type Description Value Bool Value used by the application code IOValue Bool Value of the I/O channel. IOValue and Value are equal if the channel is not forced Forced Bool Indicates whether or not the channel is forced. Status DInt Status as a integer Parameters SignalPar Measuring Range Note that the last component Parameters is itself a structured variable of type SignalPar. The data type SignalPar has the following components: Name Data Type Description Max Real Scaled max value of measuremet Min Real Scaled min value of measuremet Inverted Bool If connection is reversed Fraction Dint Number of decimals to be shown Unit String Display the physical unit 1.2 Global variables Global variables are stored in your Application root folder (under Applications) clicking it gives you the variable pop-up as seen in pic The columns are Name: every variable must have a unique name. The identifier for a variable, a function block etc. Data Type: The data type this variable is. There are several datatypes available o Basic data types: bool, int, real dword etc o I/O data types: boolio, RealIO, DwordIO o Data types defined by other software libraries. Typically consists of a collection of several other data types. Attributes: The attribute of the variable is defined. Initial value: for basic data types an initial value can be given (Eg: Boolean: ture/false) Defines the initial value of the data type. If no value is given, the default value is used. I/O address Defines the I/O address to the I/O unit. Access variables System variables that are to be accessed from a remote system with a loose connection must be declared in the Access Variable Editor. Description: In the description fields a short description can be written when declaring variables, parameters, function blocks, and data type components. 1.3 Local variables Are done in similar manner but they are defined in the application programs. 5

6 2 Function Block Diagram 2.1 FBD Editor Function Block Diagram (FBD) is a high-level graphical programming language. It describes the POUs in terms of processing elements and displays the signal flow between them, similar to electronic circuit diagrams. It represents the function block and functions by graphical symbols (boxes), their input and output parameters by pins of the boxes and the assignment of parameters by lines between the pins. A comprehensive basic range of function blocks and functions are available. The FBD editor consists of the following major parts: Execution Rules The execution order of function blocks and functions is defined at first by the order of their creation. The execution order is represented by the order of the graphic symbols (boxes) in FBD "from the left to the right" and "from the top to the bottom". You can change the execution order later by moving the selected function blocks and functions "up" or "down" within the structure pane. Just drag-and-drop the function block within the structure pane. 6

7 2.1.2 Functions in FBD The following basic functions corresponding to operators of textual programming languages are available in the FBD language: FBD Pane The FBD panes are the right upper and lower sub panes within the code pane if you are working with the FBD editor. They contain the function block diagram of the POU you are programming. NOTE! By default only the lower sub pane is shown. You can drag the separation line just underneath the variable declaration pane to access the upper sub pane. The FBD panes contain: 7

8 Graphic symbols of function and function block (boxes) Instance names of the function blocks Comments attached to the function blocks and functions Assignment of parameters in form of connection lines between the graphic symbols Comment of the page and footer Use the FBD panes to: Inspect the function block diagram of the POU you are programming Select, copy and paste functions and function blocks Create, modify and delete function blocks and functions Edit instance name of function blocks and edit comments Assign values to the parameters of function blocks and functions Toolbar Buttons There is a special toolbar in the FBD editor, with shortcuts to many of the commands found in the menu bar (or in the pop-up menus). You can see a brief explanation (tool tip) of each button, if you hold the cursor over the button. 8

9 2.1.5 Inserting a Function / Function Block There are several ways to insert a function/ function block; 1. Use the toolbar button 2. Choose Insert > Function/ Function block from the POU menu 3. Right click in the code pane and choose Insert Function / Function block Insert the Function / Function Block In the dialog window a list of available functions and function block types is presented in the drop-down list. NOTE! Just type the first letters of the function name to jump to that entry. It is also possible to use the Browse button to get an explorer-like overview of all libraries and applications and their functions / function blocks. If you want to choose from a list of previously used function block types, use the Local FB Declarations button. Connect Parameters If it is a function/function block that supports configurable input parameters, these inputs can be specified in the dialog window. To go straight to the Connection dialog window, check Connect Parameters. The EN checkbox makes the optional Enable parameter available (this is explained in the next section) EN Input Parameter The EN property for functions and function blocks in FBD makes it possible to write code that corresponds to IF statements in the Structured Text language. The EN parameter should be connected to a bool variable just as any other bool parameter. When the EN input is true, the function or function block will be executed, otherwise not. When the EN input becomes false, all outputs will keep their values from the previous cycle of execution. NOTE! If a function has an EN input, it must be connected. 9

10 The EN parameter can be turned on/off when inserting a new function or function block (see Insert Function/Function Block dialog section), or when editing the parameter properties (see below) Editing Parameter Properties Some functions or function blocks supports configurable parameters. For instance the number of inputs on an AND function can be modified. By clicking with the right mouse button on a function (box) you will see a menu. Select Edit Parameter Properties to change the size or type of the function. Activate the checkbox Enable parameter, if required. Insert / Delete Parameter Right click on a parameter (pin) of the function block or function. Select Insert Parameter to add a new, last parameter (pin). Select Delete Parameter to delete the parameter (pin). NOTE! This is only possible if the function or function block is expandable Making Connections If a parameter is to be connected to another parameter, one of them must be an output parameter and the other one an input parameter. NOTE! An output parameter can be assigned to any number of input parameters but never to another output parameter. There are basically two ways of connecting the parameters (pins) of a function or function block: Either you connect the parameters one-by-one or you connect them all at once. Connect each Parameter Separately Right click on the parameter (pin) of the function block or function (box) to which you want to assign a variable or a constant and select Connect from the context menu. 10

11 Fill in the To field with a constant value or a variable name. To display a list of all available variables, press Ctrl+J. NOTE! If you want to connect an OUT parameter to several variables, separate the names with, (comma). For example: Start1, Start2 Press OK to close the dialog window or Apply/Next to apply the connection and go the next parameter. The Direction setting together with the value in the Next: drop-down list determine what will happen when the Next button is pressed. In the example in the figure pressing Apply/Next will move the selection forward to the next unconnected parameter. If the user enters a name that is not recognized by the system (i.e. not declared) and presses OK or Apply/Next, the system will ask the user if the unknown name should be declared by the system. Access to Variables with Structured Data Types You gain access to the components by using the syntax: <main_identifier>.<component> For instance: NxxTemp is a RealIO variable. Type NxxTemp as main identifier and then a. to see the structured variables. Connect All Parameters To connect several of the parameters in one action, it is best to bring up the Parameter Connections editor. Right click and select Edit Parameter List. Fill in the name of the variable in the actual Parameter field. Use the button to get a treelike overview of the POU and its variables. Connect from one Function Block to Another To connect two parameters to each other, select one parameter (pin) by clicking on it with the left mouse button. Press the Ctrl key while clicking with the left mouse button on the other parameter (pin) that you want to connect to. NOTE! Be sure that you select one input parameter and one output parameter. 11

12 Connect to a Previous Selection To connect a parameter to another parameter, select the first parameter by clicking on it with the left mouse button. Click on another parameter (pin) that you want to connect to with the right mouse button. By this, you select the second parameter, though the selection of the first one remains, and you open the context menu. Select Connect to Previous Selection from the context menu to accomplish the connection Inverting Connections To invert inputs to a function or function block right click on the input parameter, and select Invert from the menu. A small circle (bubble) will appear on the input parameter Adding Comments It is possible to write comments to functions/function blocks and pages. Edit Comments of Function Blocks and Functions Select the function block or function to which you want to assign or edit a comment. Select Edit Comment from the context menu and type in your comment. Edit Page Comments If you want to add a comment for a page in FBD, just right click and select Edit Page Comment from the context menu Structure Pane The structure pane is the left sub pane within the code pane. It contains a list of all function blocks and functions of the current POU. Use the structure pane to: Get an overview of the POU. Select, copy and paste function blocks and functions. Create, modify and delete function blocks and functions. Edit instance name of function blocks, edit comments. 12

13 Change the pagination and page comments. Navigate within the program. Change the order of execution in the FBD code pane. The structure pane consists of the following sizable and movable columns: Item shows the type name of the function block or function with their properties in parentheses Comment shows the comment attached to the function block or function Page Comment shows the comment on the top of the corresponding Function Block Diagram page Page No is given at the first function block or function of every page of the Function Block Diagram Instance shows the name of function blocks 3 Structured Text (ST) Structured Text (ST) is a high-level programming language. It is compact, highly structured and contains a comprehensive range of constructs for assignments, function/function block calls, expressions, conditional statements, iterations and more. The code is simple to write and easy to read, because of its logical and structured layout. The compactness of the language gives an excellent overview of the code and less scrolling in the editor. 3.1 Structured Text Editor The code pane is used for writing code in Structured Text. It is a simple text editor. Tabs and spaces are used to structure the code for easy reading. The code pane may be divided into several tabs. Each tab is also referred to as Code Blocks. When the code is compiled the execution order of the code is firstly in tab order (left to right) and then from top to bottom inside the tabs. Instances of variables and function blocks are declared in the declaration pane. 3.2 Basic Language Elements This section gives a very brief review of the structured text language. 13

14 3.2.1 Assignment Statements An assignment statement assigns a value to a variable. The statement has two parts: Result := In1 AND In2 OR In3; The left hand side, before the assignment operator (:=) is called the assigned variable. The right hand side is an expression which is evaluated to give a value to the assigned variable. In the above example the expression results in a Boolean true/false value. (It is a Boolean expression). The AND and the OR are referred to as operators (In this case Boolean operators). NOTE! The := symbol is used for the assignment of operators and a statement must be ended with a semicolon. Another example of an assignment statement: AverageFlow := (Flow1 + Flow2)/2; The variable AverageFlow is assigned the value given by the result of the calculation on the right. Flow1 is firstly added to Flow2 and then the total is divided by 2. The expression on the right is a Real expression because it results in a Real value (floating point value). The symbols + and / are called arithmetic operators because they perform arithmetic operations on the variable values which follow them. 14

15 3.2.2 Comment Statements (* *) Comment according to IEC (# #) Comment that can be nested (ABB extension). It is normally not possible to have comments within comments (nested comments): (* This is not (* Inner Comment *) allowed *) However there is an alternative comment symbol that allows this: (# This is (* Inner Comment *) allowed #) This is useful for commenting out large blocks of code containing comments Operators Precedence The priority of operators decides the order of evaluation of an expression. Below is a summary of available operators, in descending priority: 15

16 If you are unsure of the evaluation order then use parenthesis to force evaluation of sub-expressions Conditional Structures There are two main groups of conditional structures of which here is presented the IF Then NOTE! A conditional statement is always concluded with END_IF; 16

17 3.2.6 Iteration Structures Several iteration constructs exist: They should be used with extreme caution. During the iteration of the loop, the CPU remains in the loop. If a loop has a large number of iterations then the normal scan time may be easily exceeded. NOTE! Only use these constructs when you know exactly how many iterations are going to be done. Operator FOR i := 0 to 15 DO Statement(s); END_FOR; WHILE Level > 80.0 DO Statement(s); END_WHILE; REPEAT Statement(s); UNTIL Boolean Expression END_REPEAT; EXIT; Description The FOR statement is used to allow a statement (or statements) to be executed repeatedly for a given number of times. The counter used in the repetition process can be used in the statements. In the example, the statements between the FOR and END_FOR will be executed 16 times. The WHILE statement is used in order to allow a statement (or statements) to be executed repeatedly while a certain condition is True. This separates it from the FOR statement. It has some similarities with the REPEAT statement. The REPEAT statement is used in order to allow a statement (or statements) to be executed repeatedly until a certain condition is True. Note that the test to exit the loop is placed at the end, so a minimum of one execution of the statement(s) will occur even if the expression is true at the time the loop is entered. Use the EXIT statement whenever you want to terminate a loop immediately and continue execution from the first line after the iteration statement RETURN Statement The RETURN statement causes immediate exit from the current code block (A tab in a program or control module or function block). No further code in that block is executed. 3.3 Functions and Function Blocks Functions Functions are called inside expressions with the following syntax: Var := FunctionName(Parameter(s)) In the example below the square root of a flow signal is calculated by using the Sqrt() function. 17

18 3.3.2 Function Blocks Function block calls do not appear in assignment statements. The call is itself a valid statement. Note that in ST, function block input parameters are listed with the := symbol and output parameters are listed with the => symbol. The example below shows the code for calling a delay off timer: The above timer function block is the same as the following in FBD form: Function blocks are declared in a similar way to variables, by giving them a name (an instance name). This name is then used to call them in the code. In the ST editor you must declare function blocks explicitly in the Function Block declaration tab in the editor by giving a name and a type: How to Declare Function Block Instances As an absolute minimum a function block instance must be given a name and a function block type: 1. Mark the Function Blocks tab in the declarations pane of the POU. 2. Type in an instance name for the function block in the Name column. 3. Type in the required function block type in the Function Block Type column. Place the cursor in the field and press Ctrl + J to see a list of all available function block types. NOTE! Function Block Types are defined in the libraries. 18

19 If the library that contains the function block type that you want has not been connected to the application then it will not appear in the list How to Call a Function Block Instance In the example below a delay off timer has been declared in the Function Block declaration tab, called MixTimer of type TOf: Four variables which will be used to connect to the function block have also been declared in the Variables declaration tab: 1. Call the function block instance by typing its instance name in the code pane followed by an opening parenthesis ( The system will then offer a dialogue for you to make connections. 19

20 2. Fill in the parameters that are to be connected to the function block instance in the parameter column by any of the following methods: Type the name of the variable to be connected directly into the Parameter field. (After a few characters the system will try to help you finish by supplying first matching variable name). 3. Use the Insert from List method by clicking on the Insert Variable icon in the menu bar or use the Insert Path from Tree Icon to browse the application for the variable: 4. Click on the Exit and Close icon in the dialogue. 5. The result (for this example) looks like: 3.4 Common Mistakes and their Error Messages Identifier, constant or opening parenthesis expected Double clicking on the error message line places the cursor at the end of the statement with the problem: Usually a missing semicolon (;)at the end of a statement. 20

21 3.4.2 Variable name is not unique Two variables have been declared with the same name. (Note that this results in two error one for each non-unique name). Note also that some other items are classed as variables by the system: Instance names for function blocks Instance names for control modules Sequence Step names Code Block names Sequence Transition names Parameters (in function block types and control module types) This means that within any POU all of the above must have unique names Identifier too long or invalid This error message is given under two circumstances: 1. Variable naming rules have been disobeyed - the name begins with a number. 2. A key word has been used - both words On and Off are reserved. 21

22 3.4.4 Undefined function block The programmer has declared the function block with the name MixTimer but has referenced MuxTimer in the code Type mismatch in assignment This occurs when the programmer has mixed data types in an assignment statement In this case the programmer has attempted to add a real and a dint to get a dint result. (You can t multiply apples with pears!) Incompatible types in expression This occurs when an operation has been attempted on different types that are not compatible for that operation: In the above a real has been added to a bool. 22

23 4 Sequential Function Charts (SFC) The Sequential Function Chart (SFC) programming language allows the user to describe the sequential behavior of the control program graphically. This is quoted as the fifth IEC language but it s not really a new language just a specialized editor for coding sequences. The SFC standard has been evolved from Grafcet, a graphical method of describing sequential behavior. A sequence is a unit with a complete sequence surrounded by an unconditional loop; the first step is reactivated when the sequence is finished. A sequence can be divided into separate types of structures. It is possible to structure the sequence view into several hierarchical levels with the subsequence function. 4.1 SFC Editor The SFC programming editor is divided into four panes, which are very similar to the other language program editors. The main difference is the structure pane, used to describe the sequential flow with steps and transitions. It is not possible to have a sequence without any steps or transitions. The sequence must consist of at least one step and one transition. 4.2 Steps and Transitions The sequence element always has a step followed by a transition. This is the smallest part of a sequence and is a complete entity. You may not have a step on its own or a transition on its own, neither can you have two steps together or two transitions together. 23

24 4.2.1 Steps A step is a basic element, which is activated by its preceding transition. The step becomes active until its succeeding transition is true, and then next step is activated. Each step has a name, that can be changed, and each step can have up to three associated set of actions. It is not possible to change the action names. The step is used to hold instructions which perform actions on the process devices. NOTE! The instructions must be programmed in the Structured Text language. Double clicking on any step will result in that step being opened in the editor: Each of the boxes represents one code block (or tab) in a program editor, written in Structured Text. There are three blocks called Entry, Active and Exit. Instructions written in the Entry block (P1 = Pulse rising edge) are executed once and once only on entry into the step. (During transition from the previous step) Instructions written in the Active block (N = Non-stored) are executed on each scan whilst the step is active. Instructions written in the Exit block (P0 = Pulse falling edge) are executed once and once only on exit from the step. (During transition to the next step) Transition The transition from one step to the next holds a Boolean expression. (Note that it is NOT a code block as such and requires a slightly different syntax). A Boolean expression is any sequence of terms and operators that results in a single Boolean result True or False. The sequence will transit from one step to the next when the transition following the currently active step goes true. 4.3 Sequence Constructs Simultaneous Sequences The simultaneous sequence structure allows simultaneous and independent execution of two or more branches of sequence actions. Each branch starts and ends with a step. The last transition cannot activate its succeeding step unless the last step of both branches is active. When the transition Tr7 becomes true, Step S7 is left and each of the three steps S8, S9 and S10 become active. When a parallel branch is left all preceding steps must be active AND the following transition must become true. In the above steps S12, S9 and S13 must be active together with Tr9 being true before the exit from the branch takes place. 24

25 4.3.2 Sequence Selection A series of transition conditions are monitored when the prior step is active. The next step to become active is determined by which transition becomes true. That branch is selected and the execution continues in that branch. The execution can only continue in one of the branches. The branch with the highest priority (graphically, the left to right branch order corresponds to the priority order) and a true transition condition will be chosen. 4.4 Jumps and Destinations Unstructured links inside the sequence structures are necessary in some cases to deal with extraordinary situations and when, for example, changing the process production mode. A jump is a link from a named single transition to a named single step, located anywhere in the same sequence structure. Multiple jumps can be connected to a step. A jump can be considered as a sequence selection. It is a transition where the execution is transferred from the preceding step to the jump destination step, when the transition condition becomes true. NOTE! It is not possible to jump between different sequences. A forward jump is typically used when some sort of exception occurs. A backward jump is typically used when a sequence loop is needed inside the overall sequence loop. 5 Control Modules Control module types and their instances represent an extension to those code containers (POU) described by IEC You can think of control modules as super function blocks that have the ability to hold code and also graphics. The coding techniques and editors are the same as for function block types and programs, with very little difference, so all the knowledge of programming with traditional programs can be carried forward into the world of control modules. However because of the addition of graphics as part of the module, the beginner must learn about a new graphics editor called the Control Module Diagram Editor (CMD Editor). Just as an FBD editor is used to build programs with function blocks, so the CMD editor is used to build applications with control modules. 25

26 5.1 Control Modules as Code Containers Control Modules are code containers that can contain: Code written in any of the five language editors Graphics configured in the CMD Editor Other control modules nesting leads to the ability to create deep hierarchies Code Code is written in a code editor which is exactly the same as that for programs. This means that the code inside control modules may be written in Structured Text, Function Block, Ladder, Instruction list or Sequential Flow Chart. Code may be separated into code blocks (tabs). In this respect there is nothing new to learn. The top pane has four tabs for the declaration of Parameters, Variables, Externals Variables and Function Blocks. It is identical to the editor for a function block type that was used in the previous sections Graphics The graphical part of a control module is written in its own editor called the Control Module Diagram Editor (CMD Editor) The graphical part is drawn within the green boundary, using the tools in the toolbox to the left. The tools available are: Graphical Primitives Text, Rectangle, Oval, Arc, and Polyline/Polygon Interaction Objects Command Button, Option Button, Check Box, Input Field, Window interaction Composite objects Image Selector, String Selector, History Graph, Bar Graph Connective Node and Graphical Connection All of these objects may be connected to variables for dynamic display and interactions by an engineer or technician. In the same way as the FBD editor is used for instantiating function blocks, the CMD editor is used for instantiating control modules. 5.2 Representation of Control Modules In general control module types are defined in libraries. These libraries are connected to applications. Instances are created in applications. The types in a connected library become available to the applications that have that library connected 26

27 Note that types are shown with green icons, whereas instances are shown with blue icons When to use what? As a general guideline, traditional programming is typically suitable for small applications whereas control modules are recommended for large applications. Control modules support object-oriented programming and code re-use to a greater extent and therefore make a large application more flexible and easier to maintain. Control modules have many advantages over traditional programs: Faster execution due to more efficient compiler Reduced memory usage in the controller Better data flow within the application ensuring that all values are updated in each scan. Provision of configurable graphics for creating diagnostics, commissioning and maintenance windows and views. Object oriented philosophy can be closely followed with control modules because they allow almost unlimited nesting without performance penalties. 5.3 Control Module Diagram (CMD) Editor The CMD editor is a tool that allows the engineer to configure the graphical representation for an application or a control module type. Any graphical component is drawn in the CMD editor. Instances of previously defined control module types are placed graphically in the application using the CMD editor. Open the CMD editor for an application by marking the respective application, and then clicking right for the context menu. 27

28 5.3.1 How to Create a Control Module Instance 1. Open the CMD editor and open the module in which the instance is to be placed. 2. Right click and select Create > Control Module 3. Select the library which contains the type that you want and select then the type. Give the instance a name (distinguish between the instance name and the type name). 4. Click OK. 5. A cursor will appear in the CMD editor, click left and drag to instantiate the module Graphical Connections Many modules have nodes available for graphical connection. Connections between nodes may be done graphically rather than explicitly declaring the variables. The diagram below shows four instances from the library ControlStandardLib suitable for creating a simple PID flow control loop: These modules are prepared with nodes and may be connected graphically. 1. Click right in the view and select Create > Graphical Connection 2. The cursor will appear. 3. Click once on the node where the connection is to start 4. Move the cursor to the destination node and double click to finish. 28