Open User Communication; Ouc Instructions - Siemens SIMATIC S7 System Manual

7.3.5

Open user communication

The Open User Communication (OUC) instructions give your program a way to
communicate over an Ethernet network to another Ethernet capable device. The other
Ethernet device can be another S7-200 SMART CPU or another third party device that
supports either UDP, TCP, or ISO-on-TCP protocol. Your program controls all aspects of the
communication from selecting the protocol, initiating the connection, sending data, receiving
data, and terminating the connection.
Note
The CPU models CPU CR20s, CPU CR30s, CPU CR40s, and CPU CR60s have no
Ethernet port and do not support any functions related to the use of Ethernet
communications.
7.3.5.1

OUC instructions

There are four Open User Communications (OUC) instructions to control the communication
process:
● TCON opens the UDP, TCP, or ISO-on-TCP (RFC 1006) connection between the
S7-200 SMART CPU and the remote device.
● TSEND and TRCV send and receive data.
● TDCON closes the connection.
Table 7- 7
LAD/FBD
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
OUC instructions
STL Description
TCON table
TCON initiates a UDP, TCP, or ISO-on-TCP communications con-
nection from the CPU to a communication partner.
TSEND table
TSEND sends data to another device.
TRECV table
TRECV retrieves data over an existing communication connection.
TDCON table
TDCON terminates a UDP, TCP, or ISO-on-TCP communications
connection.
Program instructions
7.3 Communication
217