Function Blocks - Mitsubishi MELSEC-Q Series Programming Manual

4.2.4

Function blocks

Libraries, functions, and other function blocks are used to edit function blocks.
Function blocks can be used by calling them from program blocks or function blocks. Note that
they cannot be called from functions.
Function block
Function blocks can retain the input status since they can store values in internal and output
variables. Since they use retained values for the next processing, they do not always output the
same results even with the same input values.
Function blocks can be described in the ST or structured ladder language.
● Instantiation
Function blocks need to be instantiated to be used in program blocks.
For details of instantiation, refer to the following section.
Section 4.2.7 Functions and function blocks
Instances are variables representing devices assigned to labels of function
blocks.
Devices are automatically assigned when instances are created with local labels.
Library
Function
Function block
4.2 POUs
4.2.4 Function blocks
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