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A Function Block is a group of commonly-used logic operations, combined together.
By making them a function, you can simplify the ladder logic program, and decrease processes to step required for programming.
Once you create a Function Block, you can easily place it in a logic program by dragging and dropping it.
You can protect programs from unauthorized viewing or editing, by setting passwords for Function Blocks.
Registering Function Blocks allows you to share them between projects.