18
Function Blocks
Section 1-4
1-4-2
Advantages of Function Blocks
Function blocks allow complex programming units to be reused easily. Once
standard program sections have been created as function blocks and saved
in files, they can be reused just by placing a function block in a program and
setting the parameters for the function block's I/O. Reusing standardized func-
tion blocks reduces the time required for programming/debugging, reduces
coding errors, and makes programs easier to understand.
Structured
Programming
Structured programs created with function blocks have better design quality
and required less development time.
Easy-to-read “Block Box”
Design
The I/O operands are displayed as local variable names in the program, so
the program is like a “black box” when entering or reading the program and no
extra time is wasted trying to understand the internal algorithm.
Different Processes Easily
Created from a Single
Function Block
Many different processes can be created easily from a single function block
by using input variables for the parameters (such as timer SVs, control con-
stants, speed settings, and travel distances) in the standard process.
Reduced Coding Errors
Coding mistakes can be reduced, because blocks that have already been
debugged can be reused.
Data Protection
The local variables in the function block cannot be accessed directly from the
outside, so the data can be protected. (Data cannot be changed unintention-
ally.)
Improved Reusability
through Programming
with Variables
The function block's I/O is entered as local variables, so the data addresses in
the function block do not have to be changed as they do when copying and
reusing a program section.
Creating Libraries
Processes that are independent and reusable (such as processes for individ-
ual steps, machinery, equipment, or control systems) can be saved as func-
tion block definitions and converted to library functions.
The function blocks are created with local variable names that are not tied to
physical addresses, so new programs can be developed easily just by reading
the definitions from the file and placing them in a new program.
Nesting Multiple
Languages
Mathematical expressions can be entered in structured text (ST) language.
Nesting function blocks is supported for CX-Programmer Ver. 6.0 or higher.
For example, it is possible to express only special operations in ST language
within a function block in a ladder diagram.
For details on using function blocks, refer to the CX-Programmer Ver. 7.0
Operation Manual: Function Blocks (Cat. No. W447).
Function block (ladder language)
Call (Nesting)
Function block (ST language)
Содержание CP1L-EL20DR-D
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Страница 178: ...144 Connecting the CX Programmer Section 5 1 Click the Connect button to connect and then connection online is completed...
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