7-13
7 Tag Data Link Functions
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
7-1 Introduction to Tag Data Links
7
7-1-7 Concurrency of Tag Data Link Data
Maintaining Concurrency in the Tag Data in a Tag Set
To maintain concurrency in the values of multiple tags in a tag set, the tags (variables with a Network
Publish attribute) must satisfy the following four conditions.
(1) The tags must be assigned to the same tag set (connection).
(2) A refreshing task must be set for the network variables assigned to the tags, and the
refreshing task must be the same for all tags in the tag set.*
Note If you set a refreshing task for a network variable, you must set a variable access time to allocate enough
time to access the network variable from outside of the Controller.
(3) A tag that uses AT specification must not be included in the same tag set.
(4) The variable access time set for each task must be set to a higher value than is
required to transfer the tag data. Refer to 12-3-3 Effect of Tag Data Links on Task
Periods for details on the variable access time and data transfer.
• Setting Refreshing Tasks for Tags (Network Variables)
Concurrency of the tags in the tag set is maintained.
You do not need to set a refreshing task for variables (tags) that use an AT specification because
they are updated in the primary periodic task.
NJ-series ControllerNJ-series Controller
Connection
Tag data links updated.
Refreshing task Refreshing task
EtherNet/IP
10
10
10
Value of variable
100→10
100→10
100→10
Value of variable
Variable c
Variable b
Variable a
Variable c
Variable b
Variable a
Tag set
Variable f
Variable e
Variable d
Tag set
The values of the
tags in the tag set
are refreshed at
the same time.
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