Programming in CFC

You can wire programming blocks together in the CFC Editor and create descriptive block diagrams.

The editor supports you as follows:

Creating a POU in the implementation language Continuous Function Chart (CFC)

1. Select a folder in the Solution Explorer in the PLC project tree.
2. In the context menu select the command Add > POU...
The Add POU dialog opens.
3. Enter a name and select the implementation language Continuous Function Chart (CFC).
4. Click Open.
TwinCAT adds the POU to the PLC project tree and opens it in the editor.

Insert elements and interconnect them with connecting lines

1. Position a Function block element and an Output element in the editor. Use the mouse to drag the elements from the Toolbox view into the editor.
2. Click on the output of the Function block element.
The output is marked with a red square.
3. With the mouse button pressed, draw a connecting line from the output of the Function block element to the input of the Output element.
When the input pin is reached, the cursor changes its symbol.
4. Release the mouse button.
The output pin of the function block is connected to the input pin of the output.
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Alternatively, you can select the two pins while pressing the [Ctrl] key, followed by selecting the command Connect Selected Pins in the CFC menu or the context menu.

Call instances

1. Create a new project and add a default PLC project
2. Create the function block FB_Sample in the implementation language ST with inputs and outputs:
FUNCTION_BLOCK FB_Sample
VAR_INPUT    
    nIn1 : INT;
    nIn2 : INT;
    sIn1 : STRING := 'Name';
    bIn1 : BOOL;
END_VAR
VAR_OUTPUT
    nOut : INT;
    sOut : STRING;
    bOut : BOOL;
END_VAR
VAR
END_VAR
nOut := nIn1 + nIn2;

sResult := sIn1;

IF bIn1 THEN
    bOut := TRUE;
END_IF
3. Create the program PRG_First in the implementation language ST .
4. Instantiate function blocks and declare variables:
PROGRAM PRG_First 
VAR
    nCounter  : INT;
    fbSample1 : FB_Sample;
    fbSample2 : FB_Sample;
    nResult   : INT;
    sResult   : STRING;
    bResult   : BOOL;
END_VAR
5. Drag a Box element from the Toolbox view into the editor.
6. Click on the ??? field and type ADD.
The function block type is ADD. The function block acts as an adder.
7. Click the line number 3 in the declaration editor.
The declaration line of nCounter is selected.
8. Click in the selection and drag the selected variable into the implementation. Focus an input of the ADD function block there.
An input was created, declared and connected to the function block.
9. Click again in the selection and drag the variable to the output of the ADD function block.
An output was created, declared and connected to the function block.
10. Drag from the Toolbox view an Input element into the implementation.
11. Click on its field ??? and enter 1.
12. Connect input 1 to an input on the ADD function block.
A network is programmed. At runtime, the network counts the cycles and stores the result in nCounter.
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13. Click the line number 4 in the declaration editor.
The line with fbSample1 is selected.
14. Click in the selection and drag the selected instance into the implementation.
The instance appears as a function block in the editor. Type, name and the function block pins are displayed accordingly.
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15. Drag the fbSample2 instance into the editor. Interconnect the instances with each other and with inputs and outputs.
Sample:
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A program in ST with the same functionality could look like this:

PROGRAM PRG_First_ST 
VAR
    nCounter  : INT;
    fbSample1 : FB_Sample;
    fbSample2 : FB_Sample;
    nResult   : INT;
    sResult   : STRING;
    bResult   : BOOL;
END_VAR
nCounter := nCounter + 1;
fbSample1(nIn1 := 16, nIn2 := 32, sIn1 := 'First', xItem := TRUE, nIn3 := 2, nOut => fbSample2.nIn1, bOut => fbSample2.bIn1);
fbSample2(nIn2 := fbSample1.nOut, sIn1 := 'Second', nIn3 := 2, nOut => nResult, sOut => sResult, bOut => bResult);

Creating connection marks

You have a CFC programming block with connected elements.
1. Select a connecting line between two elements.
The connecting line is selected, and the input or output of the elements is marked with a red square Programming in CFC 5:.
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2. Select the command Connection Mark in the context menu or the CFC menu.
The connection is disconnected and replaced with a connection mark - source and a connection mark - sink. The mark name is generated automatically.
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3. Click in the connection mark source.
The name can be edited.
4. Enter a name for the source connection mark.
Source connection mark and sink connection mark have the same name.
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See also:

Resolving collisions and fixing connecting lines by control points

The following example illustrates the application if the command Route All Connections, and the application of control points.

1. Position the elements input and output and link the elements.
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2. Position two function block elements on the line.
The connecting line and the function blocks are shown in red due to the collision.
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3. Select the command Route All Connections in the CFC > Routing menu.
The collision is resolved.
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4. Change the connecting lines step by step.
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The connecting line was changed manually and is now locked for auto-routing. This is indicated by a padlock at the end of the connection.
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5. Select the connecting line and select the command Create Control Point in the CFC > Routing menu. Alternatively, you can drag a control point from the Toolbox view onto a line.
A control point is created on the connecting line. The connecting line is fixed at the control point.
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6. Change the connection according to the example below.
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The control point enables you to modify the connecting line as required. You can set as many control points as you want.
7. Remove the control point with the command Remove Control Point in the CFC > Routing menu.
8. Unlock the connection with the command Unlock Connection or by clicking on the padlock symbol.
9. Select the connecting line and select the command Route All Connections.
The connecting line is drawn automatically, as shown under step 3.
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Connections within a group are not automatically routed.

See also:

Reduce representation of a function block

Requirement: a CFC programming block is open. In the editor, its function blocks are displayed with all declared connections.

1. Select a function block whose connections are partially unconnected.
Example: FB_Sample

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The function block requires space for all connections.
2. From the menu CFC > Routing, select Remove Unused Pins.
The function block requires less space and is now only displayed with the functionally relevant connections.

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