Omron NY532-5400 User Manual page 130

7 Tag Data Link Functions
(2) Tag (network variable) without a refreshing task
The values are written to the variables in a system service.
Execution
priority
High
Low
Additional Information
Relationship between Refreshing Tasks and Data Concurrency in Tag Data Links
If you do not specify a refreshing task for global variables in tag data links, the following may
occur.
1. When the data is sent for the output tag set, another task may have already written different
values before that data is sent, depending on the timing of the task.
2. When data is received by an input tag set, another task may write different values after that
data is received, depending on the timing of the task.
Therefore, to maintain the concurrency of data in tag data links, you must specify the same
refreshing task on both the output Controller and the input Controller.
This variable may
already be written
by another task
before you send
the data.
7-14
Primary period
IO UPG MC
Primary
periodic task
Priority-16
UPG
periodic task
Tag data link
service
Priority-17
periodic task
Tag data is read
from the tag set.
System
services
NY-series Controller
Refreshing
task
Tag set
Connection
Variable a
Variable b
Tag data links
updated.
Variable c
EtherNet/IP
NY-series Industrial Panel PC / Industrial Box PC Built-in EtherNet/IP Port User's Manual (W563)
IO UPG MC IO UPG MC
Task period
Task period
UPG Interrupted.
The values are written to the network variables (tags)
in a system service.
NJ/NX-series CPU Unit
Refreshing
task
Tag set
Variable d
Variable e
Variable f
IO UPG MC IO UPG MC
UPG
This variable
may be written
by another task
after you receive
the data.
Data concurrency is not maintained
unless you assign the same
refreshing task for both the output
and the input tags.