Chapter 3 PLC System Configuration & Settings Receive Address : Users can set the length of data which will be received by the local CPU module. Receive Length : Uses can set an initial device in the CPU module where data which will be received is stored. The length must be within the range between 0 and 1000 bytes. Keep Alive Timer : Users can set a maximum keep alive time for the connection. If no data is transmitted, and the keep alive period has elapsed, the CPU module will terminate the connection automatically.
The port number used by the local CPU module and the port number used by the remote device cannot be the same, and the devices where data which will be sent is stored cannot overlap the devices where data which will be received is stored. If the IP address of the remote device is 192.168.1.100, the port number used by the remote device is 65500, and the port number used by the local CPU module is 65501, the remote device and the local CPU module can transmit data through this TCP connection. If the local CPU module wants to send 10-word data to the remote device, the data will be stored in D0~D9 before the data is sent.
If the local CPU module receives 20-word data from the remote device, the data will be stored in D100~D119. If the length of data received is larger than the length set, the first 20-word data will be stored in D100~D119, and the data after the first 20-word data will be discarded. Likewise, if the length of data received is less than the length set, the data will be stored in the devices starting from D100, and the values in devices where no new data is stored will be retained. If no data is transmitted, and 30 seconds have elapsed, the CPU module will close the socket, and terminate the TCP connection. 3-205