Siemens SIMATIC S7-1500 Function Manual page 167

OPC UA communication
9.3 Using the S7-1500 as an OPC UA server
The following example shows an array data block:
Figure 9-10 Enabling PLC tags and DB tags for OPC UA tags
This array can be read completely in one pass by OPC UA clients (see Addressing nodes
(Page 135)). The check boxes at "Accessible from HMI/OPC UA" and "Writable from
HMI/OPC UA" are activated for all the components of the array.
Result: OPC UA clients can both read and write these components.
Removing write rights
If you want to write-protect a tag, deselect the "Writable from HMI/OPC UA" option for that
tag. This removes the write right for the OPC UA clients and HMI devices.
Result: Only read access by OPC UA clients and HMI devices is possible. OPC UA clients
cannot assign values to this tag and therefore cannot influence execution of the S7 program.
Removing write and read rights
To write-protect and read-protect a tag, disable the "Accessible from HMI/OPC UA" option
for that tag (checkbox not selected). This makes the OPC UA server remove the tag from its
address space. OPC UA clients can no longer see that CPU tag.
Result: OPC UA clients and HMI devices can neither read nor write the tag.
Write and read rights of structures
If you remove the read or write right for the component of a structure, the structure or the
data block cannot be written or read as a whole.
If you remove read and write rights for individual components of a PLC data type (UDT), the
rights will also be removed from any data block based on that data type!
Visible in HMI engineering
The option "Visible in HMI Engineering" applies to Siemens engineering tools. If you disable
the option "Visible in HMI Engineering" (check mark not set), you can no longer configure the
tag in WinCC (TIA Portal).
The option does not have any effect on OPC UA.
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Function Manual, 11/2019, A5E03735815-AH
Communication