SMB MAT-LC-C Series User Manual page 53

variables and returns the result of dividing the product of the first two variables by the third
variable.
Function block
A function block is a POU that provides one or more values in a program. In contrast to functions,
a function block has no return value. The declaration of a function block begins with the keyword
FUNCTION_BLOCK, and a copy or instance of the function block can be created.
Program
A program is a POU that returns several values during operation, and the program is global in the
project file. All final values of the program are retained until the next program run.
PLC_PRG
PLC_PRG is a special predefined POU, and each project file must contain such a special
program. Actually this POU is called only once per control loop.
After a new project file is created, the command "Project"→"Object Add" will be used for the
first time. The default item in the dialog box of the POU is a POU of program type named
PLC_PRG. These default settings cannot be changed.
If tasks are defined, PLC_PRG may not be included in the project, because in this case, the
timing of the program depends on the assignment of tasks.
<Note> Do not delete or rename the POU PLC_PRG (if no task configuration is used),
PLC_PRG is the main program in a single task program.
Action
Actions can be defined and assigned to function blocks and programs. Actions represent a
further execution. It can be created in other languages. Each action has a name.
Each action works with data in a function block or program, and the action is executed using the
same input/output variables and local variables.
Resource
You need resources to configure and organize project files and track variable values.
• Global variables are used in all project files or in the network.
• The library manager is used to add library files to the project.
• Log files record actions while online.
PLC Configuration configures the hardware of the programmable controller.
• Task configuration guides the work of the program through task division.
• Watch and Receive Manager to display variable values and set default variable values.
• Target system settings are used to select and, if necessary, make final configuration of the
target system.
• Workspace as an image of project options.
The target system and target system settings required to build the project in CODESYS may also
use the following resources:
• Sample trace for graphical display of variable values.
• Parameter manager for exchanging data with other controllers in the same network.
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