Omron CP1H CPU UNITS - PROGRAMMING 05-2007, Operation Manual

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Function Blocks
Section 1-5
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)