OPC UA communication
9.3 Using the S7-1500 as an OPC UA server
Communication
Function Manual, 11/2019, A5E03735815-AH
169
9.3.2.3 Coordinating write and read rights for CPU tags
Definition of write and read rights in the information model (OPC UA XML)
In the OPC UA information model, the attribute "AccessLevel" regulates access to tags.
AccessLevel is defined bit by bit:
Bit 0 = CurrentRead and Bit 1 = CurrentWrite. The meaning of the bit combinations is as
follows:
● AccessLevel = 0: no access
● AccessLevel = 1: read only
● AccessLevel = 2: write only
● AccessLevel = 3: read+write
Example of the assignment of write and read rights (read+write)
Definition of write and read rights in STEP 7
When you define tags, you specify the access rights using the properties "Accessible from
HMI/OPC UA" and "Writable from HMI/OPC UA".
Example of the assignment of write and read rights
Figure 9-13 Example of the assignment of write and read rights
Interaction between write and read rights
If you have imported an OPC UA server interface and AccessLevel attributes are set in this
OPC UA XML file, the write and read rights are defined by the following rule: The least
extensive access rights for each setting apply.
Example
● AccessLevel = 1 (read only) in the OPC UA server interface
● Both "Accessible from HMI/OPC UA" and "Writable from HMI/OPC UA" are selected in
the PLC tag table
Result: This tag can only be read.
To Next Page
Loading...
Need help?
General
