Accessing Opc Ua Server Data - Siemens SIMATIC S7-1500 Function Manual

9.3.2.5

Accessing OPC UA server data

High performance in line with application
OPC UA is designed for the transfer of a high volume of data within a short period of time.
You can increase the performance significantly if you do not access individual PLC tags, but
rather read and write arrays and structures as a whole.
It is fastest to access arrays. Therefore, you should combine the data for OPC UA clients
into arrays.
Recommendations for access to the OPC UA server by the OPC UA client
● For one-off or infrequent data access, use standard read/write access.
● For cyclic access to small amounts of data (up to ca. every 5 seconds), use subscriptions.
Optimize the settings for the smallest publishing interval and the smallest sampling
interval at the OPC UA server.
● If you access specific tags regularly (recurring access), you should use the functions
"RegisteredRead" and "RegisteredWrite".
Allow a greater communication load for the PLC by increasing the value for "Cycle load due
to communication". Make sure that your application still works properly with the changed
settings.
Procedure for creating an array DB
You can create arrays for example in global data blocks, in the instance data block of a
function block or as an array DB . The following sections describe how to create an Array-
DB.
To create a data block with an array (array data block), follow these steps:
1. Select the CPU with the OPC UA server in the project tree.
2. Double-click "Program blocks".
3. Double-click "Add new block".
4. Click "Data block".
5. Select a unique name for the data block and accept the name that is already entered.
6. Select the "Array DB" entry from the drop-down list for "Type".
7. Select the data type for the individual components of the array from the drop-down list for
"Array data type".
8. Enter the high limit of the array for "Array limit".
9. Click "OK".
Communication
Function Manual, 11/2019, A5E03735815-AH
OPC UA communication
9.3 Using the S7-1500 as an OPC UA server
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