Siemens SIMATIC S7-1500 Function Manual page 95

Open User Communication
6.11 Secure Open User Communication
5. Create one of the instructions TSEND_C, TRCV_C or TCON in the program editor.
6. Interconnect the CONNECT parameter of one of the instructions TSEND_C, TRCV_C or
TCON with the tags of the data type TCON_QDN_SEC.
In the example below, the CONNECT parameter of the TCON instruction is
interconnected with the tag "DNS connectionSEC" (data type TCON_QDN_SEC).
Figure 6-14
Additional information
You can find more information on the TCON_QDN_SEC system data type in the STEP 7
online help.
For additional information on secure communication, refer to the section Secure
Communication (Page 34).
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TCON instruction
Function Manual, 11/2019, A5E03735815-AH
Communication