DeviceNet is a CAN-based digital industrial fieldbus used to connect PLCs, remote I/O, sensors, motor drives, valve manifolds and other field devices. DeviceNet uses CAN — Controller Area Network — at its data-link layer and CIP — Common Industrial Protocol at its upper layers. The technology is part of the CIP network family maintained by ODVA.

In simple terms: DeviceNet allows a PLC or industrial controller to communicate with many field devices over one network. The DeviceNet cable can also distribute 24 VDC network power to suitable devices, helping reduce separate wiring for low-power sensors and I/O modules.

How does DeviceNet work?

The lower communication layer of DeviceNet is based on CAN — Controller Area Network. CAN handles the fundamental frame transmission and bus-access mechanisms, while DeviceNet adds the higher-level CIP structure required for industrial devices, configuration, diagnostics and I/O communication.

DeviceNet should therefore not be described simply as “CAN with a different cable.” CAN provides the underlying data-link technology, while DeviceNet defines how industrial devices expose their identity, parameters and I/O information through CIP.

Within an industrial communication architecture, DeviceNet has traditionally been used close to the field level for devices such as sensors, distributed I/O, actuators and variable frequency drives.

What is CIP in DeviceNet?

CIP — Common Industrial Protocol is the object-oriented protocol architecture used at the upper layers of DeviceNet. The same CIP family is also used by EtherNet/IP and other ODVA technologies.

CIP defines common objects and services for device identity, configuration, parameters, I/O data and diagnostics. This common application architecture is an important relationship between DeviceNet and EtherNet/IP, even though their physical networks are very different.

Are DeviceNet and CANopen the same?

No. DeviceNet and CANopen both use CAN technology underneath, but they are different higher-level industrial communication systems.

CANopen uses concepts such as its object dictionary, PDOs, SDOs and network-management services. DeviceNet instead uses the CIP object and messaging model. A CANopen device and a DeviceNet device cannot communicate simply because both are connected to CAN_H and CAN_L. A suitable gateway or device supporting both protocols is required.

Which wires are used in a DeviceNet cable?

A standard DeviceNet cable can carry both network communication and device power using separate conductor pairs. Common wire colors are:

White: CAN_H communication signal.
Blue: CAN_L communication signal.
Red: V+ network power.
Black: V− network power.
Drain conductor: Cable shield connection.

The CAN data pair and the DC power pair are separate conductors within the DeviceNet cable. Communication data and 24 V power are not superimposed on the same two wires.

Can DeviceNet devices be powered from the network cable?

Yes, when the device is designed for network power. DeviceNet can distribute up to 24 VDC through the network cable. Depending on cable type and network design, the trunk can support currents up to 8 A.

This can simplify installation for low-power sensors, remote I/O and similar field devices. Higher-power equipment such as motor drives or solenoid systems normally uses separate load power while its communication electronics remain connected to DeviceNet.

A DeviceNet power system must be designed according to total current consumption, cable type, supply location and voltage drop. The presence of 24 V on the network does not mean an unlimited number of devices can be powered from one point.

What are trunkline and dropline in DeviceNet?

DeviceNet uses a defined trunkline-dropline topology. The trunkline forms the main network backbone, while devices can connect directly to the trunk or through shorter drop cables and taps.

This is not exactly the same wiring concept as a simple serial daisy chain. DeviceNet specifically permits defined taps and drop lines, but their length must remain within the limits established for the selected network data rate and cable type.

The maximum length of an individual DeviceNet drop is 6 m — 20 ft. The permitted total cumulative drop length changes with network speed.

Which data rates does DeviceNet support?

Classic DeviceNet supports three standard network data rates:

125 kbit/s
250 kbit/s
500 kbit/s

Higher data rates reduce the maximum permitted network length. For thick round DeviceNet cable, the standard design values are:

125 kbit/s: up to 500 m trunk length.
250 kbit/s: up to 250 m trunk length.
500 kbit/s: up to 100 m trunk length.

These figures apply to thick round cable. Thin round and flat DeviceNet cable have different length limits, so network distance should not be calculated from baud rate alone.

How many devices can be connected to DeviceNet?

A DeviceNet network supports up to 64 nodes. Node addressing uses MAC IDs in the range 0–63, and every device on the same network requires a unique address.

If two devices are configured with the same MAC ID, a duplicate-address condition can prevent normal network operation. When replacing an old field device, both its MAC ID and data-rate configuration should therefore be checked.

How is DeviceNet terminated?

The DeviceNet trunkline requires termination at its two physical ends. The ODVA installation specification uses 121 Ω, 1%, 1/4 W terminating resistors connected between CAN_H and CAN_L.

Termination should not be installed at every node. Too many termination resistors alter the electrical loading of the CAN network and can prevent reliable communication.

When diagnosing intermittent errors, the termination resistance should be checked together with CAN_H/CAN_L continuity, network power, shield connections and the physical trunk/drop layout.

What are DeviceNet I/O Messaging and Explicit Messaging?

DeviceNet supports different communication methods for different types of information. I/O Messaging is used for regular control and process data with relatively low protocol overhead. DeviceNet can use mechanisms such as polled, cyclic and change-of-state I/O communication.

Explicit Messaging is typically used for less frequent operations such as configuration, parameter access and diagnostics.

For example, operating status and command data from a motor drive may be exchanged cyclically as I/O data, while reading or changing one of the drive's configuration parameters can use explicit messaging.

What is a DeviceNet EDS file?

EDS — Electronic Data Sheet is a device-description file used by engineering and configuration software to identify a DeviceNet product and describe its communication and parameter capabilities.

When a new DeviceNet device is added to a scanner configuration, its EDS file may be registered in the engineering software. The EDS does not replace network configuration: MAC ID, data rate, connection type and I/O mapping still need to be configured correctly.

What is the relationship between DeviceNet and EtherNet/IP?

The key relationship is CIP. Both DeviceNet and EtherNet/IP use the Common Industrial Protocol at the application level, but their lower network technologies are different.

DeviceNet runs CIP over a CAN-based fieldbus at 125, 250 or 500 kbit/s. EtherNet/IP carries CIP using standard Ethernet and IP networking technologies.

Because both belong to the CIP family, gateways and controllers can be used to integrate legacy DeviceNet field devices into a newer EtherNet/IP architecture. An existing DeviceNet installation does not necessarily have to be completely removed simply because the upper-level control network has migrated to Ethernet.

Is DeviceNet still used today?

Yes. DeviceNet has a large installed base in factory automation, material handling and older machine-control systems. ODVA continues to publish DeviceNet specifications, installation information and troubleshooting documentation.

Ethernet-based industrial networks are often preferred for new systems, but replacing a stable DeviceNet installation solely because the technology is older may not be economical. Spare-part availability, machine downtime, engineering effort and modernization cost should all be considered.

Existing DeviceNet drives, I/O modules and sensors can also be connected to newer control architectures using suitable DeviceNet-to-EtherNet/IP gateways or scanner modules.

Why does a DeviceNet network fail to communicate?

DeviceNet troubleshooting should begin at the physical network, not only in the PLC program. Reversed or broken CAN_H/CAN_L conductors, incorrect termination, excessive trunk/drop lengths or insufficient network power can all prevent communication.

Next verify the network data rate and MAC ID of every device. All nodes must operate at the same DeviceNet data rate, and every node needs a unique MAC ID.

If the physical network is healthy, inspect the scanner configuration, EDS registration, connection size and PLC input/output mapping. A device may appear online while its I/O data remains incorrect because the configured connection size does not match the real device assembly.

Cable routing and shielding also matter in panels containing motors, contactors and variable frequency drives. Differential CAN signalling provides good noise immunity, but it cannot compensate for every poor EMC installation practice.

Practical DeviceNet troubleshooting checklist

1. Are all devices configured for the same 125, 250 or 500 kbit/s data rate?

2. Does every node have a unique MAC ID?

3. Are 121 Ω termination resistors installed only at the two physical ends of the trunk?

4. Are CAN_H, CAN_L, V+ and V− wired correctly?

5. Is adequate network voltage available at the most distant devices?

6. Do trunk and drop lengths comply with the selected data rate and cable type?

7. Does the scanner configuration and EDS file match the actual device?

8. Are the I/O connection size and PLC mapping correct?

Related Industrial Communication Guides

Industrial Communication · CANopen · EtherNet/IP

Related Automation Pages

PLCs · HMI Panels · SCADA · Sensors · AC Drives and VFDs