Communication
11.2 PROFINET
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
843
The TRCV_C instruction is executed asynchronously and implements the following functions
in sequence:
1. Setting up and establishing a communications connection:
TRCV_C sets up a communication connection and establishes this connection if the
EN_R parameter = "1" and there is no communication connection. Once the connection
has been set up and established, it is automatically maintained and monitored by the
CPU.
The connection description specified at the CONNECT parameter is used to set up the
communications connection. The following connection types can be used:
– TCON_Param structure for the TCP, ISO-on-TCP, and UDP protocols
– With V4.1, TCP / UDP: Connection description via the structure TCON_IP_v4 at the
parameter CONNECT
– With V4.1, ISO-on-TCP: Connection description via the structure TCON_IP_RFC at
the parameter CONNECT
An existing connection is terminated and the connection which has been set up is
removed when the CPU goes into STOP mode. To set up and establish the connection
again, you must execute TRCV_C again with EN_R = "1".
If EN_R is set to "0" before the communications connection has been established, the
connection will be established and remain in place even if CONT = "0". However, no data
will be received (DONE will remain "0").
For information on the number of possible communication connections, please refer to
the technical specifications for your CPU.
2. Receiving data via an existing communications connection:
Receipt of data is enabled when the EN_R parameter is set to the value "1". As described
above, the communications connection is established first. The received data is entered
in a receive area. You specify the length of the receive area either with the LEN
parameter (if LEN <> 0) or with the length information of the DATA parameter (if LEN =
0), depending on the protocol variant being used. If you use purely symbolic values at the
DATA parameter, the LEN parameter must have the value "0".
If EN_R is set to "0" before data is received for the first time, the communication
connection will remain in place even if CONT = 0. However, no data will be received
(DONE will remain "0").
3. Terminating the communications connection:
The communications connection is terminated after data has been received if the CONT
parameter had the value "0" when connection established was started. Otherwise, the
communications connection will be maintained.
If the receive job executes successfully, the DONE parameter is set to "1". The
communications connection may be terminated before this (see the above description of the
dependency on the CONT parameter).
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