Omron NJ Series - Page 200

6-13
6 Programming
NJ-series CPU Unit Software User’s Manual (W501)
6-2 POUs (Program Organization Units)
6
6-2-5 Details on Function Blocks
A function block consists of a function block definition that is made in advance and instances that are
then used in the actual programs. All instances of a function block are based on the function block defi-
nition.
A function block definition consists of an algorithm and a local variable table.
 Function Block Instance
When you place an instance of a function block definition in a program or another function block, the
function block definition is treated as a part of that program or function block.
Function block definitions that are called from a program or another function block are called
instances.
Every instance of a function block has an identifier known as an instance name associated with it,
and every instance uses memory.
You can create instances of a function block definition to process different I/O data in the same way.
Instances cannot be read from other programs or function blocks. If an instance with the same name
as another instance is placed in a different program or another function block, that instance will oper-
ate as a completely separate instance.
Function Block Definitions and Instances
Instance name
Instance name
Algorithm
FB1
FB1_1
Algorithm
FB1
FB1_2
Program POU
Variable
declarations
Variable
declarations
Memory area
Memory for
instance
FB1_2
Memory for
instance
FB1_1
Function block definition name
Memory area
reserved.
Function block definition name
Memory area reserved.