4
Deployment
4.1 Basics DeviceNet
DeviceNet is an open low-end network that is based upon the phys-
ical properties of CAN bus. The bus is also used to supply the
devices with the required DC 24V power. You can use DeviceNet to
install direct connections between your control system and simple
industrial devices like sensors and switches as well as technologically
advanced devices like frequency converters and barcode readers.
Direct interfacing improves communications between the different
devices and provides important diagnostic facilities at the device
level.
n
DeviceNet is an open device net standard that satisfies the user
profile for industrial real-time system applications.
n
The DeviceNet protocol has an open specification that is the prop-
erty of and administered by the independent vendor organization
"Open DeviceNet Vendor Association" ODVA.
n
This is where standardized device profiles are created to provide
compatibility and exchangeability on logical level for simple
devices of the same type.
n
In contrast to the classical source-destination model, DeviceNet
uses a modern producer/consumer model that requires data
packets with identifier fields for the identification of the data.
n
This approach caters for multiple priority levels, more efficient
transfers of I/O data and multiple consumers for the data.
n
A device that has data to send
produces
the data on the network
together with an identifier. All devices requiring data listen for
messages. When devices recognize a suitable identifier, they act
and
consume
the respective data.
n
DeviceNet carries two types of messages:
–
I/O messages
Messages that are subject to critical timing constraints and
that are contain data for control purposes that can be
exchanged by means of single or multiple connections and
that employ identifiers with a high priority.
–
Explicit messages
These are used to establish multi-purpose point-to-point com-
munication paths between two devices, which are used for the
configuration of network couplers and for diagnostics pur-
poses. These functions usually employ identifiers of a low pri-
ority.
n
Messages that are longer than 8byte are subject to the fragmenta-
tion service. A set of rules for master/slave, peer-to-peer- and
multi-master connections is also available.
n
DeviceNet employs a screened five-core cable as data communi-
cation medium. DeviceNet uses voltage differences and for this
reason it exhibits less sensitivity to interference than a voltage or
current based interface.
n
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 con-
nect redundant power supplies to the network that guarantees the
power supply when required.
General
DeviceNet
Communication
medium
VIPA System SLIO IM 053DN
Deployment
Basics DeviceNet
HB300 | IM | 053-1DN00 | GB | 15-33
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