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(2) FL-net protocol
The FL-net consists of the following 6 protocol layers.
Application layer
FA link protocol layer
Transport layer
Network layer
Data link layer
Physical layer
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.
Controller interface
Service function
Cyclic transfer
Message transfer
Token function
UDP
IP
Ethernet
(Compatible with IEEE802.3)
FA link protocol
7-7
Chapter 7: Computer Link Function
FL-net
protocol
7
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