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9.2
OPC UA variables
9.2.1
Description of the variables
OPC UA variables represent a simple way to query information from the communications
modules or make settings on the communications modules. Almost all OPC UA clients
support variables. However, you need to observe the following points when using variables:
The restriction of the update rate by the "Sampling" interval and by the "Publishing" interval
is common to all OPC UA variables. These are fundamental OPC mechanisms that can
define the intervals at which the values can be updated or queried via OPC UA. If the
intervals at which the values for a variable are updated from a process should be shorter
than the defined intervals, values can be overwritten before the query by an OPC UA client.
This problem is worsened by the use of logically related variables. If it is not possible to
determine in time that related variables can be queried completely by the client before
variables are written with new values again from the process, usage is not possible. If a
client supports events, make sure that these are used. The effects described above cannot
occur with events.
9.2.2
ExecuteScan
Table 9- 4
Path
Data type
Access
Description
Possible values
SIMATIC RF166C
Operating Instructions, 12/2019, C79000-G8976-C578-01
ExecuteScan
Root/Objects/DeviceSet/Read_point_x/RuntimeParameters/Exec
uteScan
Boolean
R/W
Indicates whether the read point is currently scanning for tran-
sponders or allows the scan process to be activated/deactivated.
Query of the current status:
•
•
Set:
•
•
TRUE: Read point scans for transponders.
FALSE: Read point does not scan for transponders.
TRUE: The scan process of the read point for transponders is
activated.
FALSE: The scan process of the read point for transponders
is deactivated.
Programming via OPC UA
9.2 OPC UA variables
105
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