Function Blocks

Define function blocks in the Function Blocks section of the . Program functions using Function Block Diagram (FBD), Ladder Diagram (LD), Sequential Function Chart (SFC), or Structured Text (ST).

Specify these properties for function blocks:

Function Block Properties
Property	Description
Code Generation
Generate Debug Info	Generate information required for debugging using step-by-step execution.
Generate Monitoring Symbol	For graphical program organization units (POUs), generate information required for graphically displaying the output values of elements when debugging or simulating
Instance Symbols Extra Bytes	Size of memory reserved for each function block instance for adding symbols monitoring information during updates. A string-type output takes up 260 bytes.
Info
Comment	Plain text
Description	Rich text
Full Name	(Read-only) Full name of the function indicating the project and controller to which it belongs
Language	(Read-only) Programming language of the POU
Name	(Read-only) Name of the function block. Function block names are limited to 128 characters beginning with a letter followed by letters, digits, and single underscores. The last character for a function block name must be a letter or digit; function block names cannot end with an underscore character. Reserved words, defined words, or data types, such as elementary, structures, or arrays are not valid names. The same type of elements within a scope must have unique names.
Order	Position of the function block within the execution order
Password Protected	(Read-only) Function is protected by a password controlling its access
Path	(Read-only) Complete path where the function block files are stored on the computer

When adding function blocks, define required parameters. Function blocks can have a maximum of 128 parameters (inputs and outputs). When defining parameters, consider these limitations:

Parameter names are limited to 128 characters beginning with a letter followed by letters, digits, and single underscores. The last character for a parameter name must be a letter or digit; parameter names cannot end with an underscore character. Reserved words, defined words, or data types, such as elementary, structures, or arrays are not valid names. The same type of elements within a scope must have unique names.

Possible data types for parameters are BOOL, SINT, USINT, BYTE, INT, UINT, WORD, DINT, UDINT, DWORD, LINT, ULINT, LWORD, REAL, LREAL, TIME, DATE, STRING, Array types, Structure types, Function blocks

For String type variables, string capacity is limited to 255 characters excluding the terminating null character (0), a byte for the current length of the string, and a byte for the maximum length of the string

For user defined addresses, the format is hexadecimal and the value ranges from 1 to FFFF

For dimensions, example: [1..10] for a one dimensional array, [1..4,1..7] for a two dimensional array

For instances of function blocks, reset the initial values defined for individual instances.

Perform these tasks for function blocks:

Function Block Tasks
Task	Procedure
Add a function block	In the Application View , right-click the Function Blocks element, point to Add Function Blocks , and then select the programming language for the function block. To define the parameters for the function block, right-click the function block, and then select Parameters .
Export a function block	Export function blocks as exchange files (.pxf). Also export functions from libraries. In the Application View , right-click the function block, and then select Export... . In the Save <Function Block> As dialog box, browse for the location in which to store the function block exchange file, and then select Save . TIP:* If a user-defined structure contains user-defined structures, create at least one variable for each user-defined structure to support a successful POU export.
Add a function block from an exchange file	Import function blocks previously saved as exchange files (.pxf). For program organization units (POUs) in version control, check out the POU before importing the exchange file (.pxf). Avoid renaming POUs in the Import dialog box when importing. Renaming may cause a loss of function block references or broken binding links for local variables. Rename the POU from the Application View . In the Application View , right-click the Function Blocks element, point to Add Function Blocks , and then select Existing Function Block... . In the Select Exchange File dialog box, locate the exchange file containing the function, and then select Open . In the Add Existing Function Block dialog box, select the element to import, and then select Import .
Reset the initial values of function block instances	In the Application View , right-click the function block, then point to Refactor , and then select Reset Initial Values of Instances. From the Refactoring dialog box, select the function block instances to reset, and then select OK .
Copy and paste a function block	In the Application View , right-click the function block, and then select Copy . Right-click the Function Block element, and then select Paste .
Rename a function block	In the Application View , right-click the function block, then select Rename , and then type a name for the function block.
Delete a function block	In the Application View , right-click the function block, and then select Delete .