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Communication partner
● Process access
For process access you need a station in productive operation, alternatively:
– S7 station
– Modbus station
● Cloud access / OPC clients
– For cloud access, you need the access set up to a cloud broker.
– You need at least one set up OPC UA client for connection via OPC.
Requirements in the S7 stations
Writing values to outputs
• Outputs and PLC tags
• DB tags
The following requirements need to be met in your STEP 7 project or in the connected S7
stations.
● Tags / symbols
For access to the process data by referencing to tags of the CPU, tags or symbols must
be created in the relevant CPU.
Write access via the MQTT Subscriber function of the gateway is only possible in DB tags
of the CPU.
STEP 7 Professional: The "Optimized block access" option must be disabled in DBs.
The tags of the CPU must be marked as follows for use by OPC UA services (options
selected):
– "Accessible from HMI/OPC UA"
– "Writable from HMI/OPC UA"
For further details, see section Data points (Page 101).
SIMATIC CC7
Operating Instructions, 10/2019, C79000-G8976-C503-02
WARNING
When referencing to outputs and PLC tags with write access, note that the values are
written immediately to the outputs of the CPU without first being processed by the user
program.
Writing values has a direct influence on the process.
When referencing to DB tags, written values are only used when processed by the user
program.
Required for write access
Application and functions
1.7 Scope of delivery and requirements
21
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