Omron NJ-series User Manual page 137

5 Designing Tasks
Tasks and Operating Modes
The relationship between CPU Unit operating modes and tasks is given in the following table.
Task
Primary periodic task
Periodic tasks
Event tasks
Precautions for Correct Use Precautions for Correct Use
• Even if the execution condition for an event task is already met when you change the operating
mode to RUN mode, the event task will not be executed. An event task is executed only when
its execution condition changes from not met to met during RUN mode.
• Even in RUN mode, an event task is not executed if there is a major fault level error.
The Processing Performed in Each Task
 Primary Periodic Task
The primary periodic task has the highest execution priority. It executes processes with high speed
and high precision.
In every period, this task performs system common processing, I/O refreshing, user program execu-
tion, and motion control. Unlike periodic tasks, the primary periodic task performs motion control
processing (MC).
I/O refreshing
Refreshing
*1: Task period
*2: Task execution time
Processing
I/O refresh- Output data
ing processing
Refreshing
Input data
processing
System common process-
ing 1
5-10
• These tasks are executed in both RUN mode and PROGRAM mode.
• The user program is executed only in RUN mode.
Event tasks are executed only in RUN mode.
*1
Task period = Primary period (fixed)
*2
Task execution time (varies)
Control processing
User program
execution
The CPU Unit executes tasks in this fixed period. This is a preset, fixed time.
This is the actual time it takes from the point that the execution condition is
met until execution is completed.
• Output refresh data is created for Output Units that refresh I/O.
• If forced refreshing is set, the forced refreshing values are reflected in the output
refresh data.
• This process exchanges data with I/O.
• Input refresh data is loaded from Input Units that refresh I/O.
• If forced refreshing is set, the forced refreshing values are reflected in the input
refresh data that was read.
• Processing for exclusive control of variables in tasks (when accessing tasks are
set)
• Motion input processing is performed.
• Data trace processing (sampling and trigger checking) is performed.
• Event task condition expressions are judged.
Specification
Processing contents
*1
NJ-series CPU Unit Software User's Manual (W501)