Mitsubishi Electric MELSEC iQ-F Series - Page 24

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3 PROGRAM ORGANIZATION UNITS
3.3 Function Blocks (FB)
Ex.
Structure of instance for nested function block
The instance of FB2 declared as a local label is secured in the local label area, local latch label area, and signal flow for FB of
FB1 which is the declared source.
When an FB type local label to FB1 is added in the above example, since the capacity of the reserved area is 48 words for
local label area, 16 words for local latch label area, and 8 words for signal flow for FB, all programs are required to be
converted (reassigned) to add a function block with an area exceeding the capacity.
bLabel0
FB2_a
INCP wLabel0
wLabel1
FB2
WORD
bLabel0
VER
VER
bLabel1 BIT VER
bLabel2 BIT VER
wLabel0 WORD VER_RETAIN
bLabel0 BIT VER
bLabel1
bLabel2
wLabel1
FB2
bLabel1
bLabel2
wLabel1
wLabel1
bLabel1
wLabel0
bLabel0
bLabel0
INC wLabel0
wLabel1 WORD VER_OUTPUT
bLabel1 BIT VER_INPUT
wLabel0 WORD VER
bLabel0 BIT VER_INPUT
bLabel1
wLabel1MOVP wLabel0
wLabel0
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
Creating an
instance based on
FB1 definition
FB1 instance structureFB1 instance structure
Padding size
3 words
Padding size
2 words
Reserved area 16 words
Reserved area 48 words
FB2 area
52 words
Signal flow for FB
8 words
Signal flow for FB
Reserved area 8 words
FB2 definitionFB2 definition
Ladder program (FB2)
Local label definition (FB2)
Label name
Data type
Reserved area (FB2)
Area Size
Local label area
Local latch label area
48 words
16 words
Signal flow for FB 8 word
Padding size 1 word
Reserved area 48 words
FB1 area
104 words
Reserved area 16 words
FB1 area
36 words
FB2 area
16 words
Reserved area 8 words
For MOVP (4 bits)
For INCP (3 bits)
FB2 area
9 words
FB1 area
18 words
Class
FB1 definitionFB1 definition