5-1
Section
Overview of FINS Communications
62
5-1
Overview of FINS Communications
The FINS communications service enables client control of operations such as
reading or writing server PC memory area data without the need to program
these operations into the server PC user program. The Ethernet Unit uses a ded-
icated UDP/IP port to execute the FINS communications service. (Refer to FINS
UDP Port Number under 4-2-1 Settings.)
5-1-1 Communications On an Ethernet Network
Data is sent and received as UDP packets on an Ethernet network. The FINS
port number (default value: 9600) set in the CPU Bus Unit System Setup is used
for FINS communications. (Refer to 4-2 CPU Bus Unit System Setup.)
Ethernet header
IP header
UDP header
FCS
UDP (User Datagram Protocol) packet
PC
Ethernet Unit
or host computer
UDP packet (FINS command)
Ethernet
UDP packet (FINS response)
Ethernet Unit
PC
FINS frame
When a FINS command is issued from the Ethernet Unit, the IP address is found
from the FINS address specified by CMND(490). For details, refer to 3-1 Before
Operation.
Note The UDP/IP protocol does not provide communications control to ensure com-
munications reliability. Consequently, the FINS communications services using
the UDP/IP protocols cannot guarantee that any message arrived safely and un-
altered at the destination. Methods to ensure reliability, such as retries and ap-
propriate processing of FINS responses, must be programmed into the user ap-
plication.
5-1-2 FINS Communications Service Features
The FINS communications service is a function for controlling operations such
as sending and receiving data, changing modes, and so on, between nodes on
OMRON factory automation networks. It provides the following features.
•
Communications instructions are executed in the user program.
•
Writing data, changing modes, reading detailed information about Units, and
so on, can be executed without any particular knowledge of communications
procedures or network classification.
