Chapter 7: Computer Link Function

(2)FL-net protocol

The FL-net consists of the following 6 protocol layers.

Application layer

 

 

 

 

 

 

 

 

 

Controller interface

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cyclic transfer

Service function

 

 

 

FA link protocol layer

 

 

 

 

 

 

 

 

 

 

Message transfer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Token function

 

 

FL-net

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

protocol

Transport layer

 

 

 

 

 

 

 

 

 

 

UDP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Network layer

 

 

 

 

 

 

 

 

 

 

IP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Data link layer

 

 

 

 

 

 

 

 

 

Ethernet

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Compatible with IEEE802.3)

 

 

 

Physical layer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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

7

The FL-net data transfer system has the following features.

1It manages the transmission of data using the Master-less Token method, and prevents commu- nication conflicts.

2It 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.

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