DeviceNet™ System/CAN Description
 

DeviceNet™ is a low-cost communications protocol that eliminates hard wiring and connects industrial devices such as limit switches, photoelectric sensors, valve manifolds, motor starters, process sensors, bar code readers, variable frequency drives, panel displays and operator interfaces to a network. DeviceNet’s direct connection provides improved communication between devices, as well as important device-level diagnostics not easily accessible or available through hard-wired I/O interfaces.

DeviceNet™ is based on the Controller Area Network (CAN) broadcast-oriented communication architecture. CAN uses a bus arbitration method (CSMA/BA) that ensures the highest priority message is given preference in the event of a data collision. The DeviceNet™ protocol further defines message priorities such that I/O messages are given top priority and configuration messages have lower priority.

A DeviceNet™ network supports up to 64 nodes and virtually an unlimited amount of I/O. The bus uses a trunkline/dropline topology, where bus power and communication are supplied on a single cable. Bus power is 24 VDC and supplies current to operate the nodes and, typically, the power input devices. Some Turck stations require an additional 24 VDC auxiliary power to supply current for outputs.

DeviceNet™ allows peer-to-peer data exchange (where a DeviceNet™ node can initiate communication with other nodes or peers), and a master/slave configuration in which the master node initiates all communication and all other nodes, or slaves, respond to the master node’s requests.