Technical data

2.2.2 Network Access Technique
The medium access technique in SINEC L2/L2FO complies with the token
bus technique for active stations and master-slave technique for passive
stations as stipulated in DIN 19245 Part 1.
Active stations
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can send data to other stations without being requested to
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can request data from other stations.
Passive stations
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can only send data after a request from an active station.
Whether or not a station is active or passive depends on the particular
device. Simple field devices, e.g. motor controllers are usually passive,
"intelligent" devices such as programmable controllers, on the other hand,
are normally active. Many devices can be assigned an active or passive
role. The CP 5430 TF/CP 5431 FMS can only be assigned parameters as
an active station.
The access technique is not dependent on the transmission medium.
Fig. 2.2 illustrates the hybrid technique with active and passive stations.
This is explained briefly below:
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All active stations form the logical token ring in a fixed order, each
active station being aware of the other stations and their order in the
logical ring.
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The token (right to transmit) is passed from active station to active
station. The following applies to all active stations: a token rotation
takes place between transmitting the token and receiving it again.
System Overview B8976060/02
Volume 1 2 - 10