The DeviceNet fieldbus is based on the CAN protocol (Control Area Network). Designed as a low-cost, yet efficient bus system for the lowest field bus level, it ensures the networking of sensors, actuators and associated controls. The main application is the factory automation.
Background of DeviceNet
DeviceNet was originally developed by Allen-Bradley, Rockwell Automation, and later handed over from the marketing as open fieldbus standard to the ODVA (Open DeviceNet Vendor Association). Today it is standardized according to the European standard EN 50325.
ControlNet and Ethernet/IP belong together with DeviceNet to the CIP Networks (Common Industrial Protocol). Whereby ControlNet represents the cellular level, Ethernet/IP the control level and DeviceNet the field level.
According to the producer-consumer communication model the DeviceNet device can be the the client (Master) or the server (slave). Whereby the client and the server, in turn, may be Producer, Consumer or both.
The Technology of DeviceNet
A maximum of 64 nodes per network segment is assigned a unique address. Here the addresses of the network nodes (0 to 63) can be adjusted by means of rotary or DIP switches.
The transmission speed is either 125 Kbps, 250 Kbps or 500 Kbps. The baud rate can be adjusted with a rotary or DIP switches.
On the lower layers (1-4) the open network standard DeviceNet uses the CAN specifications of the OSI model. CAN is characterised by collosion free technique at Layer 2 (Data Link Layer) to avoid communcation faults in case of 2 nodes sending data simultaneously.
In the upper layers (5-7), it uses the Common Industrial Protocol defined by the ODVA. This layer allows a universal connection of automation components from the field level to the Ethernet. Thus, the real-time data from the field devices for applications such as mobile data acquisition and parameterization are available.
DeviceNet USB Interface
For the access on a DeviceNet network Thorsis Technologies offers an USB adapter, which can be adapted by an open API for customization of existing applications. The functionality as Explicite Messaging Server is thus feasible as well as the functionality as Explicite messaging client or the process data exchange via “Poll”, “Bit Strobe” “Cyclic” and “Change of State” connections.