Lenze I/O system 1000 System Manual - Manual (Page 558)

DeviceNet communication
About DeviceNet
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558 EDSIO1000 EN 7.0
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 method
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.