8 DeviceNet communication
8.1 About DeviceNet
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Lenze · I/O system 1000 · Reference Manual · DMS 5.0 EN · 09/2016 · TD17
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Transmission medium
DeviceNet employs a screened five-core cable as data communication medium. DeviceNet uses
voltage differences and for this reason it exhibits less sensitivity to interference than a voltage or
current based interface.
Signals and power supply conductors are included in the same network cable. It is therefore possible
to connect devices that obtain the operating voltage via the network as well as devices with an
integrated power supply. Furthermore it is possible to connect redundant power supplies to the
network that guarantees the power supply when required.
DeviceNet employs a master line/tap line topology with up to 64 network nodes. The maximum
distance is either 500m at a rate of 125kbit/s, 250m at a rate of 250kbit/s or 100m at a rate of
500kbit/s.
The length of the tap lines can be up to 6m while the total length of all tap lines depends on the
baud rate.
Network nodes can be removed from or inserted into the network without interruption of the
network operation. New and failed stations are detected automatically.
Bus access procedure
DeviceNet operates according to the Carrier-Sense Multiple Access (CSMA) principle, i.e. every
station on the network may access the bus when it is not occupied (random access).
The exchange of messages is message orientated and not station orientated.
Each message is provided with a unique and prioritising identifier. At any time only one station is
able to occupy the bus with its messages.
The DeviceNet bus access control is subject to non-destructive, bit-wise arbitration. In this case non-
destructive means that the successful station participating in the arbitration does not need to re-
send its message. The most important station is selected automatically when multiple stations
access the bus simultaneously. If a station that is ready to send recognises that the bus is occupied,
its send request is delayed until the current transfer has been completed.
Addressing
All stations on the bus must be uniquely identified by means of an ID address. Every DeviceNet
device has addressing facilities.
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