3 PROGRAM ORGANIZATION UNITS
3.3 Function Blocks (FB)
21
3
Instances
■Instances
An instance is a label assigned to realize a function block definition. Multiple instances can be created from one function block
definition.
An instance consists of the following items.
Structure of instance (Example of subroutine type function block)
For the local label area and local latch label area, since the label area is secured in units of four words, three-words (padding
size) are secured in the above example.
Each area occupies a reserved area. The reserved area is used to add or change the local label, instructions, or instances of
the function block while keeping the label assignment by conversion or online change. If the area of the target data type to be
added cannot be secured, all programs are required to be converted (reassigned).
Item Description
Local label area Used to assign the local label of the function block.
Local latch label area Used to assign the latch attribute local label of the function block.
Signal flow area (Signal flow for FB) Used to assign the signal flow for the instruction in the function block definition.
bLabel0
bLabel0
INCP wLabel0
wLabel0
BIT
WORD
bLabel0
wLabel0
VER
VER_RETAIN
FB1 definitionFB1 definition
Ladder program (FB1)
Local label definition (FB1)
Label name Data type Class
Reserved area (FB1)
Area Size
Local label area
Local latch label area
Local label area
Local latch label area
48 words
16 words
FB1 instance structureFB1 instance structure
Padding size
3 words
Padding size
3 words
Reserved area 16 words
20 words
Reserved area 48 words
52 words
Signal flow for FB
8 words
Reserved area 8 words
9 words
For LD(2 bits)
For INCP(3 bits)
Another instance of FB1Another instance of FB1
Creating another
instance based on
FB1 definition
(same area size)
Local label area
Local latch label area
Signal flow for FB
Creating an
instance based on
FB1 definition
Signal flow for FB
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