DeviceNet is an application-level protocol used in the automation environment. DeviceNet was originally developed by Allen-Bradley, a Rockwell Automation brand. They later turned it into an open network. It is currently managed by ODVA (Open DeviceNet Vendors Association). DeviceNet is a communication tool that enables logical conversation between a PLC (Programmable Logic Controller). This communication includes flow meters, level sensors, motors, etc.
Many controllers communicate via a DeviceNet browser rather than speaking as discrete modules.
DeviceNet follows the OSI model. It uses the three upper layers of CIP (Common Industrial Protocol) in the layer. The lower four layers are adapted to DeviceNet. The physical layer consists of cables. The data link layer uses the CAN (Controller Area Network) standard. This standard manages traffic between devices. DeviceNet's network and transport layers communicate with the device and access the MAC and message ID of each device. The advantage of this connection ID is that it detects duplicate MAC addresses on connected devices and notifies the user. There are 5 types of cables in DeviceNet: 3 round and 2 straight. These cables are available in thick, thin, class 1 round and KwikLink flat and lite subtypes. Round cable can be used on trunk or drop lines. Cables use twisted pair wire. As the line gets longer, the data rate drops to between 500-125kbps. Terminating resistors of 0.25 watts or greater are placed at both ends of the line. These resistors are connected directly to the signal wires. Resistors reduce the electrical noise of the line. If they are not, DeviceNet will not work properly. Drop lines connect devices to the main line. The drop line length determines the data rate. The total drop length for each data rate is known as 125kbps-512ft, 250kbps-256ft, 500kbps-128ft. You can connect the main line to devices using multiple types of connectors and taps. Devices can be connected directly to these connectors or as branches or chains.
This choice of connection type will affect the line length calculation. On the software side, DeviceNet is an interface for configuring our network. Allen-Bradley developed RSNetworx to map and assign addresses to all devices on the network. The table layout is done to match the RSNetworx network and then the configuration is set on all devices. The DeviceNet browser is a piece of hardware located in the PLC chassis. It talks to the PLC from behind the chassis. DeviceNet uses EDS(Electronic Data Sheets) to identify a device or commission it from the network. As for the advantages of DeviceNet, they can be listed as ubiquity, low cost, reliability, and efficient use of network bandwidth and power available in the network. Disadvantages include limited bandwidth, message size and maximum cable length. In DeviceNet, 90 percent of all problems are caused by a cabling issue or the absence of an EDS file.