Omron CJ1W-EIP21 Operation Manuals page 144

7 Tag Data Link Functions
• Not Setting Refreshing Tasks for Tags (Network Variables)
Concurrency of the tags in the tag set is not maintained.
NJ-series Controller
Refreshing task
Value of variable
100 → 10
Variable a
100 → 10
Variable b
100 → 10
Variable c
 The timing of updating network variables that are assigned to tags is
synchronized with the execution period of the program that accesses the
network variables.
Set the refreshing task for the network variables assigned to the tags to the task that contains the
program that accesses those network variables.
• Difference between the Operation of Tags with a Refreshing Task and Tags without a Refreshing
Task
When you set a refreshing task for tags (network variables) that is the same as the task that con-
tains the program that accesses them, those tags are refreshed at the same time as the execution
of the program. Refreshing of tags (network variables) that have no refreshing task is handled by
the system service with the lowest execution priority, and therefore it is not synchronized with the
execution of the program.
Execution
Primary period
priority
High
Primary
periodic task
Priority-16
periodic task
Priority-17
periodic task
Low
System service
7-14
Tag set
Connection
Variable a
Variable b
Tag data links updated.
Variable c
EtherNet/IP
(1) Execution timing of the program
(2) Refresh timing of network variables (tags) with the primary periodic task* set as the refreshing task*
(3) Refresh timing of network variables (tags) that do not have the primary periodic task set as the refreshing task
(1) (2) (1) (2)
IO UPG MC IO UPG MC
IO UPG
UPG
*: Refreshed during system common processing 2 in the task processing.
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
NJ-series Controller
Refreshing task
Tag set
Variable d
Variable e
Variable f
(1) (2) (1) (2)
IO UPG MC IO UPG MC
Task period
Task period
Value of variable
The
values of
Refreshed.
10
tags in
the tag
set are
Refreshed.
10
not
refreshed
Not refreshed.
100 at the
same
time.
(1) (2)
IO UPG MC
IO UPG
(3)
.....
The system service is executed
during free time between task execution.