Function Blocks (Fb) - Mitsubishi Electric MELSEC iQ-R Series Programming Manual

3.3

Function Blocks (FB)

A function block is a POU called and executed by program blocks and other function blocks.
Function
block
Unlike a function, a function block does not have a return value.
A function block can hold values in variables and thus can hold input states and processing results.
A function block uses the value it holds for the next processing and therefore it does not always output the same result even
with the same input value.
Ladder program
A function block needs to be instantiated to be used in programs.
Page 22 Instances
• For details on standard function blocks, refer to the following.
MELSEC iQ-R Programming Manual (Instructions, Standard Functions/Function Blocks)
• For details on process control function blocks, refer to the following.
MELSEC iQ-R Programming Manual (Process Control Function Blocks)
• For details on module function blocks, refer to the following.
Function Block Reference for the module used
3 PROGRAM ORGANIZATION UNITS
20
3.3 Function Blocks (FB)
Function
block
FB
FBD/LD program
(1)
(2)
(3)
(4)
Program
block
FB
Program
block
FB
(1) Instance name
(1)
(2) Function block name
(2)
(3) Output variable
(4) Input variable
(3)
(4)