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06.91
2
Local Area Networks
As automation in manufacturing increases, so does the necessity to exchange data between
different manufacturing systems such as controls, robots, conveyor systems and higher-level
systems as for instance host computers.
In the past, information was transferred between the individual systems by people. This
method is time-consuming and prone to errors.
Local area networks (LANs), interconnecting all systems involved in the manufacturing and
planning process, provide a remedy for this problem. LANs ensure secure and quick data
transfer within manufacturing facilities as well as to higher-level systems.
Special requirements must be met by LANs in the tough environment of industrial
manufacturing:
•
A universal basis for different stations (terminals)
•
Insensitivity to external mechanical and electric stresses
•
High availability
•
Simple extendability
Various configurations are possible for local area networks. They are different in the type of
connection and of data transmission.
For the computer link with SINUMERIK 8X0, bus and star connections are of special
importance. These are described below in greater detail.
2.1
Bus connection
Networks with bus architectures generally use serial data transmission and often a time-
division multiplex method to maintain the data flow. The bus topology has the following
advantages:
•
Passive transport medium, only needs a coaxial cable terminating with the correct
impedance;
•
Depending on the allocation procedure, the network control is concentrated at one station
or distributed over all connected stations;
•
Easy reconfiguration, stations can be connected or disconnected as desired;
•
The failure of one station does not affect the operation of the network, provided the
allocation method is suited for the purpose.
The only disadvantage of the bus topology is that it uses a common transport medium: if the
cable is damaged, all nodes are affected.
Suitable transport media for local networks are:
•
twisted copper lines,
•
coaxial cables,
•
broad band coaxial cables
•
fibre optic cables.
The bus consists of a common resource, the bus cable, and branches to each station.
© Siemens AG 1989 All Rights Reserved
SINUMERIK 840/880 (PJ)
6FC5 197-0AB20-0BP0
2 Local Area Networks
2.1 Bus connection
2–1
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