Siemens SIMATIC S7-1500 Function Manual page 313

Connection resources
11.2 Allocation of connection resources
Connection resources for HMI communication
With HMI communication, the occupation of connection resources in the station depends on
the HMI device being used.
Table 11- 2
HMI device
Basic Panel
Comfort Panel
RT Advanced
RT Professional
If you do not use system diagnostics or alarm configuration, the station occupies only one connec-
1
tion resource per HMI connection.
Example: You have configured the following HMI connections for a CPU 1516-3 PN/DP:
● Two HMI connections to an HMI TP700 Comfort. (2 connection resources each)
● One HMI connection to an HMI KTP1000 Basic. (1 connection resource)
In total 5 connection resources are occupied for HMI communication in the CPU.
Connection resources for OPC UA client communication
Each connection that the OPC UA client of the CPU has established to an OPC UA server
occupies a connection resource in the station.
When establishing and closing an OPC UA connection, the OPC UA client temporarily
occupies an additional connection resource. According to RFC 793, this connection resource
is released again after a wait of approx. 60 seconds.
Note
Lack of resources due to temporary connection resources
A lack of connection resources occurs in the following situation:
• The OPC UA client of the CPU establishes or closes several connections simultaneously.
• The number of available connection resources of the station is insufficient for permanent
and temporary connection resources of the OPC UA client communication.
Ensure that there are always enough available connection resources in the station to
establish and end OPC UA connections.
Measures:
• Plan enough reserve for the OPC UA client connections.
• If necessary, establish or close the OPC UA connections one after the other.
312
Maximum occupied connection resources for different HMI devices
Maximum occupied connection resources of the
station per HMI connection
1
2
1
2
1
3
Function Manual, 11/2019, A5E03735815-AH
Communication