DeviceNet is a sensor/actuator bus system, which is internationally standardized (EN50325) and based on CAN (Controller Area Network). DeviceNet supports a number of communication types for the input and output data:
- Polling: the master module (“scanner”) sends the output data cyclically to the assigned devices and receives the input data in an answer telegram.
- Change of State: Telegrams are sent as soon as their contents have changed.
- Cyclic: The modules send the data automatically after a cycle time has elapsed.
- Strobed: The scanner requests the input data using a broadcast telegram to all the devices.
The DeviceNet devices in the Fieldbus Box series support all these types of I/O communication.
DeviceNet devices are parameterized using acyclic services (Explicit Messaging). The effective utilization of the bus bandwidth allows DeviceNet, particularly in change of state mode, to achieve short system reaction times in spite of the relatively low data rates.
The Beckhoff DeviceNet devices have a powerful implementation of the protocol. Through active participation in the ODVA’s technical committees, Beckhoff is contributing to the further development of this bus system, and has in this way itself gathered profound DeviceNet expertise. The fieldbus modules for DeviceNet are available as standard variant (B520) or optionally with integrated tee-connector (B528). This makes the fieldbus wiring much easier. Straight or angled versions of pre-assembled plugs or field-assembled plugs can be used.
The node address is set in the range from 0 to 63 using two decimally coded rotary switches. The transmission rate set at the DeviceNet scanner determines the speed of the system and is recognised automatically by the DeviceNet box (auto baud rate). “Electronic Data Sheets” (*.eds files) for DeviceNet configuration tools are available. Special I/O parameters not covered by the DeviceNet standard can be set by means of the KS2000 software (serial connection to the configuration interface of the Fieldbus Box) or via acyclic explicit messages.
The extensive diagnostic functions of the Beckhoff DeviceNet devices allow rapid fault localization. The diagnostic messages are transmitted over the bus and collated by the master. The status of the network connection, the device status, the status of the inputs and outputs and of the power supply are displayed by LEDs.
Compact Box modules for DeviceNet are available for all relevant industrial signals. In addition to digital and analog input and output modules including thermocouple and RTD inputs, there are also incremental encoder interfaces available for displacement and angle measurement in addition to serial interfaces to solve a large number of communication tasks.
The DeviceNet Coupler Box gathers the I/O data from the Extension Box modules over the interference-free IP-Link fibre optic cable. It detects the connected modules and automatically allocates the input and output data to the process image. Both data consistency and a clear separation of input and output data are ensured. The Coupler Box has four digital inputs and four digital outputs. Other kinds of signals are available in the Extension Box.