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Chapter 7: Computer Link Function
7
(2) FL-net protocol
The FL-net consists of the following 6 protocol layers.
FL-net
protocol
FA link protocol
Note: The transport layer and network layer use the UDP/IP addressing scheme. The data link layer
and physical layer use the Ethernet scheme.
(3) Features of the FL-net transfer system
The FL-net data transfer system has the following features.
1 It manages the transmission of data using the Master-less Token method, and prevents commu-
nication conflicts.
2 It is possible to specify a certain refresh cycle interval as the FL-net circulates a Token.
3 The specified Token is transmitted together with the cyclic data.
4 When starting up, the FL-net sends a token from the node with the lowest node number.
5 When a token is not received within a certain interval, the next node sends a token.
6 By using the Master-less Token method, even if some nodes are faulty the network will not stop
operating.
7 The FL-net has an information management table for items such as the operation mode (RUN/
STOP) / hardware error (ALARM), so that it can inform other nodes of the operation status.
Application layer Controller interface
FA link protocol layer
Cyclic transfer
Service function
Message transfer
Token function
Transport layer UDP
Network layer IP
Data link layer
Ethernet
(Compatible with IEEE802.3)
Physical layer