Program Blocks; Functions - Mitsubishi MELSEC-Q Series Programming Manual

4.2.2

Program blocks

A program block is an element that is stated at the highest level of POU. Libraries, functions, and
function blocks are used to edit program blocks.
Program block
Sequence programs executed in a programmable controller CPU are created by program blocks
of POU.
For a simplest sequence program, only one program block needs to be created and registered to
a task in order to be executed in a programmable controller CPU.
Program blocks can be described in the ST or structured ladder language.
4.2.3

Functions

Libraries and functions are used to edit functions.
Functions can be used by calling them from program blocks, function blocks or functions.
Function
Functions always output same processing results for same input values.
By defining simple and independent algorithms that are frequently used, functions can be reused
efficiently.
Functions can be described in the ST or structured ladder language.
4.2 POUs
4-6
4.2.2 Program blocks
Library
Function
Function block
Library
Function