8
Function Blocks Section 1-2
Reduce Coding Errors Coding mistakes can be reduced because blocks that have already been
debugged can be reused.
Data Protection The variables in the function block cannot be accessed directly from the out-
side, so the data can be protected. (Data cannot be changed unintentionally.)
Improved Reusability with
Variable Programming
The function block’s I/O is entered as variables, so it isn’t necessary to change
data addresses in a block when reusing it.
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 variable names that are not tied to actual
addresses, so new programs can be developed easily just by reading the def-
initions from the file and placing them in a new program.
Compatible with
Multiple Languages
Mathematical expressions can be entered in structured text (ST) language.
1-2-3 Function Block Structure
Function blocks consist of function block definitions that are created in
advance and function block instances that are inserted in the program.
Function Block
Definitions
Function block definitions are the programs contained in function blocks. Each
function block definition contains the algorithm and variable definitions, as
shown in the following diagram.
1. Algorithm
Standardized programming is written with variable names rather than real I/O
memory addresses. In the CX-Programmer, algorithms can be written in
either ladder programming or structured text.
tim_a TIMER
tim_b TIMER
ON_TIME INT
OFF_TIME INT
TIMX tim_a OFF_TIME
tim_b
TIMX tim_b ON_TIME
tim_a
ENO
Name
Type
Internal
Internal
Input
Input
Function Block Definition
Example: CLOCK PULSE
Algorithm
Example: CLOCK PULSE
1. Algorithm
2. Variable Definitions
Variable definitions
Usage
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