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Section 1 Specifications
1-8 Program Organization Units (POUs)
The program organization units include functions (FCTs), function blocks (FBs), and programs (PGs).
Programs are programmed by the user. Functions and function blocks may be supplied by the manufacturer or made by the user.
<Types of program organization units>
No program organization unit can be defined recursively. No function block can be called from a function. However, functions
can be called from a function block.
<Types of callable POUs>
<Number of variables that can be used in a POU>
Program User function
User function block
VAR
15000
1024 words (Note 2)
Number of words occupying the user FB
instance area
Total words:
Main unit with 14/24 points: 1536 words
Main unit with 32/40/60 points: 3072 words
VAR_INPUT
–
256 words
(No. of terminals: max. 128)
VAR_OUTPUT
–
–
VAR_IN_OUT
–
–
VAR_EXTERNAL
15000
–
15000
(Note 1)
Notes:
1) One VAR_IN_OUT declaration uses two words.
2) Depends on the size of temporary memory used by program.
(1024 words - Size of temporary memory used by all programs)
Total of the size of temporary memory used by individual program
System function
User function
System function block
User function block
Program organization unit (POU)
Program (PG)
Function (FCT)
Function block (FB)
Program (PG)
User function block
User function
System function
User function
System function block
User function block
System function
User function
System function block
User function block
System function
User function
