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Overview of Communications Functions Section 1-5
Executing, from the host computer, FINS commands with UDP/IP or TCP/IP
headers enables various control operations, such as the reading and writing
of I/O memory between PLCs, mode changes, and file memory operations.
For example, it is possible to connect online via Ethernet from FINS communi-
cations applications such as the CX-Programmer, and to perform remote pro-
gramming and monitoring. (See note.)
Note Use CX-Programmer version 4.0 to use TCP/IP. For lower versions of CX-Pro-
grammer, FinsGateway Version 2003 or higher is required to use TCP/IP.
The FINS gateway function enables access to PLCs on not only the same
Ethernet network but on various other networks, including SYSMAC LINK and
Controller Link.
Upgraded Functions With the CS1W-ETN21 and CJ1W-ETN21, the following functions have been
upgraded.
• The FINS communications service can be executed not only with UDP/IP
but also with TCP/IP, and it is even possible to use FINS communications
with both UDP/IP and TCP/IP together on the same network. Using TCP/
IP makes FINS communications highly reliable.
• Even if the IP address and UDP port number of the host computer (a
DHCP client computer) are changed, it is still possible for the host com-
puter to send FINS commands to PLCs on the Ethernet network and to
receive responses. When UDP is used, either the automatic generation
(dynamic) method or the IP address table method must be selected for IP
address conversion. When TCP is used, changes in IP address and TCP
port numbers are handled automatically.
• Multiple FINS applications (CX-Programmer and user-created application
programs) at the same computer can be connected online to a PLC via
Ethernet (using either TCP/IP or UDP/IP).
1-5-2 Socket Services
The socket services allow devices on the Ethernet to send and receive vari-
ous data using either the UDP or TCP protocol.
Manipulating Dedicated
Control Bits
One way to use socket services is to set the required parameters in the
parameter area allocated in the DM Area, and then to request particular UDP
or TCP socket services by turning ON dedicated control bits in memory. When
the Ethernet Unit has completed the requested process, the same bit is
turned OFF to provide notification. Data that is sent or received is automati-
cally handled according to the I/O memory locations specified in the parame-
ter area.
There is no need to execute the CMND(490) instruction or to monitor the com-
pletion timing and actual processing of the instruction, so this helps to simplify
ladder programming.
Ethernet
Ethernet Unit
IP
UDP or TCP
FINS
CS/CJ-series
CPU Unit
