Omron CJ Series Connection Manual page 38

9.1.1. Communications Data Flow
The following figure shows the data flow from when the PLC issues the command data with
TCP socket communications to the destination device until when the PLC receives the
response data from the destination device. This program continuously executes a series of
processing from the TCP open processing to the close processing. The receive processing is
repeated when the response data is divided and multiple receive data are sent. No response
data may exist depending on the destination device and send command. In this case, skip the
response receive processing by setting the receive processing not required setting in
advance.
*Receive processing required/not required setting...
-Receive processing required: After the send processing, the program waits for the receive data and shifts to the receive
processing.
-Receive processing not required: After the send processing, the program immediately shifts to the close processing.
1. TCP open processing
2. Checking the connection
3. Sending a command
*When the receive processing required
setting is set, the program waits for the
response data.
4. Receiving a response
*When multiple response data are received,
the receive processing is repeated.
*When the receive processing not required
setting is set, the program skips the receive
processing.
5. Logout processing
6. Close processing
The Ethernet Unit issues a TCP open request to the
destination device, and establishes a TCP
connection.
↓
The Ethernet Unit receives the result of the automatic
login processing from the destination device, and
confirms the result (OK).
↓
The Ethernet Unit issues the send message, which is
set in the ladder program, to the destination device,
and receives the response data.
↓
The Ethernet Unit stores the response data, which
was received from the destination device, in the
specified internal memory of the CPU Unit.
↓
The Ethernet Unit issues a LOGOUT command (BYE)
to the destination device, and terminates the
communications processing.
↓
The Ethernet Unit issues a close request to the
destination
connection.
device, and terminates
9．Program
the TCP
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