Siemens SIMATIC S7-1200 Manual page 131

As shown in the following example, you can also use individual TSEND and TRCV
instruction to communication over a connection created by a TSEND_C or TRCV_C
instruction. The TSEND and TRCV instructions do not themselves create a new connection,
so must use the DB and connection ID that was created by a TSEND_C, TRCV_C or TCON
instruction.
Easy Book
Manual, 11/2011, A5E02486774-04
Easy to communicate between devices
① TSEND_C on CPU_1 creates a
connection and assigns a connection
ID to that connection (ID=1).
②
TRCV_C on CPU_2 creates a
connection and assigns the
connection ID to that connection on
CPU_2 (ID=1).
③
TSEND and TRCV on CPU_1 use the
connection ID created by the
TSEND_C on CPU_1 (ID=1).
TSEND and TRCV on CPU_2 use the
connection ID created by the TRCV_C
on CPU_2 (ID=1).
7.5 PROFINET
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