DeviceNet
is one of three open network standards (DeviceNet, ControlNet and
EtherNet/IP), all of which use a common application layer, the "Common
Industrial Protocol" (CIP). This common application layer and open
software and hardware interfaces allow for a universal connection of
automation components from the fieldbus level over the control level to
the enterprise level.
The Family of CIP Networks is specified and published by ODVA (Open DeviceNet Vendor Association - http://www.odva.org) and CI (ControlNet International - http://www.controlnet.org).
The Common Industrial Protocol presents communication and application
in the object model. Predefined objects facilitate the data exchange
between different devices and manufacturers. By creating various device
profiles, additional standardisation benefiting the user was achieved.
CIP is a connection based protocol. It defines the exchange of I/O data
using I/O Messaging (or Implicit Messaging) as well as the exchange of
general data for configuration, diagnostic and management via Explicit
Messaging. CIP thus provides 4 essential functions to the user:
- Common object model for application
- Common communication model for data exchange in the network
- Common configuration methods
- Common device profiles
DeviceNet is the implementation of CIP over CAN (Controller Area Network).
The
DeviceNet specification standardises the physical connection of
DeviceNet nodes by defining Layer 4, Layer 3 (DeviceNet Transport),
Layer 2 (Usage of CAN), Layer 1 and Layer 0 (Physical Layer and
Transmission Media). Along with specifying connectors, cable types and
cable lengths, communication-based displays, operating elements and the
corresponding housing labelling are also defined.
A
DeviceNet network can run up to 64 nodes with baud rates of 125, 250 or
500 kBaud. The maximum length of a DeviceNet network can be up to 500 m
(at 125 kBaud and usage of suitable cables). The devices can either be
supplied via the DeviceNet network (nominal 24 V) or have their own
power supply.
The
main field of application of DeviceNet is factory automation with
I/O-modules, valves, encoders, simple drives and controls (PLC). Within
the Family of CIP Networks DeviceNet covers the main part of the
applications where small to medium amount of data with short to medium
cycle times (1 ms to 500 ms) can be exchanged in the network.
Classic Master/Slave applications are supported by the Predefined Master/Slave Connection Set.
The Unconnected Message Manager Port (UCMM) and the dynamic creation of
connections for Explicit Messages and I/O Messages were specified for
more complex slave devices and the support of Peer-to-Peer networking. |
