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Procedures Section 3-2
Function Block Definitions
Creating Function Block
Definitions
One of the following windows will be displayed when the newly created Func-
tion Block 1 icon is double-clicked (or if it is right-clicked and Open is selected
from the popup menu). A variable table for the variables used in the function
block is displayed on top and an input area for the ladder program or struc-
tured text is displayed on the bottom.
Ladder Program
Structured Text
As shown, a function block definition consists of a variable table that serves
as an interface and a ladder program or structured text that serves as an algo-
rithm.
Variable Table as an Interface
At this point, the variable table is empty because there are no variables allo-
cated for I/O memory addresses in the PLC.
Ladder Program or Structure Text as an Algorithm
• With some exceptions, the ladder program for the function block can con-
tain any of the instructions used in the normal program. Refer to 2-3
Restrictions on Function Blocks for restrictions on the instructions that
can be used.
• Structured text can be input according to the ST language defined in
IEC61131-3.
Using OMRON FB Library
Files
Double-click the inserted function block library (or right-click and select Open
from the pop-up menu) to display the variable table that has finished being
created at the top right window, and the ladder program that has finished
being created in the bottom right window. Both windows are displayed in gray
and cannot be edited.
Variable table
Ladder input area
Variable table
ST input area
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