Omron NJ Series User Manual

5-13
5 Designing Tasks
NJ-series CPU Unit Software User’s Manual (W501)
5-2 Task System
5
5-2-4 Event Task Execution Conditions
 Event Tasks
An event task is executed only once when the specified execution condition is met. You can use 0 to
32 event tasks. The processing details for event tasks are shown in the following figure.
*1 Refer to 5-2-13 Ensuring Concurrency of Variable Values between Tasks for details on exclusive control.
An event task is executed only once when the specified execution condition is met. There are the follow-
ing two types of execution conditions for event tasks.
*Refer to Execution Timing When the Execution Condition Is a Condition Expression for a Variable on page 5-19
for the timing of when the value of the specified variable is checked to see if the specified condition expression is
met.
When the ActEventTask (Execute Event Task) instruction is executed in the user program, the specified
event task is executed once. Refer to the NJ-series Instructions Reference Manual (Cat. No. W502-E1-
05 or later) for the detailed specifications of the ActEventTask instruction.
Using the ActEventTask instruction to execute event tasks makes it easy to see which event tasks are
executed. Also, this method is also effective when the execution condition for the event task may
change before meeting the condition expression for the variable is determined.
Processing Processing contents
System common pro-
cessing 1
• Processing for exclusive control of variables in tasks (when accessing tasks are
set)
*1
User program execution • Programs assigned to tasks are executed in the order that they are assigned.
System common pro-
cessing 2
• Processing for exclusive control of variables in tasks (when refreshing tasks are
set)
*1
5-2-4 Event Task Execution Conditions
Execution condition Event task execution timing Reason for use
Execution with the ActEvent-
Task instruction
When ActEventTask instruction is
executed
• When you need to explicitly specify which
event tasks to execute in the user pro-
gram
• When the execution condition for the
event task may change before meeting
the condition expression for the variable
is determined
Execution when a condition
expression for a variable is
met
When the specified variable value
matches the specified condition
expression
*
When you want to simplify the user pro-
gram by executing event tasks without user
programming
Executing Event Tasks for the ActEventTask Instruction
* The CPU Unit will temporarily interrupt the
execution of a task in order to execute a
task with a higher execution priority.
Task execution time (varies)
User program User program
executionexecution
User program
execution
Control processing
**
System common processing 2 System common processing 1
Task execution
condition is met.

Omron NJ Series Specifications

General

Brand	Omron
Model	NJ Series
Category	Controller
Language	English