Omron NX-SID Series - Differences between Programs, Functions, and Function Blocks; Details on Programs

7 - 5
7 Programming
NX-series Safety Control Unit User’s Manual (Z930)
7-1 POUs (Program Organization Units)
7
7-1-3 Differences between Programs, Functions, and Function Blocks
The hierarchical relationships between programs, functions, and function blocks are shown in the fol-
lowing figure.
Programs consist of a local variable table and an algorithm. The algorithm is programmed in the FBD
language. You can use any instructions or user-defined function blocks in the algorithm.
7-1-3 Differences between Programs, Functions, and Function Blocks
Programs Function blocks (FBs) Functions (FUNs)
Type
User-defined only Instructions or user-defined Instructions only
(User-defined functions not
supported.)
Execution method
Executed upon execution
of the safety task.
Called from a program or
another function block.
Called from a program or
function block.
Algorithm
All Instructions Supported. Supported. ---
User-defined
function blocks
Supported. Supported.
Execution conditions
Always executed. Always executed.
Specify the execution con-
dition with an input vari-
able.
Always executed.
7-1-4 Details on Programs
Program Structure
Function
blocks
Task
Program 1
Program 2
Functions
Functions
Functions
Function
blocks
Assigned.
Task
Safety
program
Safety
program
Program
Local variable table
Algorithm
Function blocks
Functions