DeviceNet
DeviceNet is a digital, multi-drop fieldbus network protocol designed for industrial automation, enabling the interconnection of controllers, sensors, actuators, and other I/O devices to facilitate data exchange and control in manufacturing environments.[1] It adapts the Common Industrial Protocol (CIP) to the Controller Area Network (CAN) physical and data link layers, providing a robust, cost-effective solution for device-level networking.[2] Originally developed by Allen-Bradley and publicly released in 1994, DeviceNet was transferred to the Open DeviceNet Vendor Association (ODVA) in 1995 for ongoing standardization and management, resulting in millions of nodes deployed globally since the mid-1990s.[3][2] At its core, DeviceNet employs a trunkline-dropline topology that integrates both signal and power distribution over the same cable, typically using 24 Vdc at up to 8 amps, which simplifies wiring and reduces installation costs compared to traditional point-to-point systems.[1] The network supports up to 64 nodes per segment and operates at baud rates of 125 kbps, 250 kbps, or 500 kbps, with maximum cable lengths reaching 500 meters at the lowest speed using thick round cable.[4] Communication follows the OSI model, with CAN handling layers 1 and 2 for reliable, prioritized messaging, while CIP manages upper layers (3-7) through a producer-consumer model that enables efficient, cyclic I/O data exchange (implicit messaging) alongside configuration and diagnostics (explicit messaging).[2] This architecture supports peer-to-peer interactions, commander/responder setups, and features like QuickConnect for hot-swapping devices without network disruption.[1] DeviceNet's adoption stems from its interoperability, ensured by ODVA conformance testing and vendor-neutral specifications, allowing seamless integration across diverse equipment from multiple manufacturers.[4] It is particularly suited for factory automation applications, including motor control, safety systems, energy management, and human-machine interfaces (HMIs), where it reduces cabling complexity and enables distributed control.[2] The protocol's use of standardized cabling options—such as thick or thin round cables and flat cables—along with mini- and micro-style connectors, further enhances its flexibility in harsh industrial settings.[4] Internationally recognized under IEC 62026-3, DeviceNet continues to serve as a foundational technology in the CIP family, promoting unified communication in automation ecosystems.[4]Overview
Definition and Purpose
DeviceNet is a digital, multi-drop fieldbus network protocol designed for interconnecting industrial controllers, sensors, actuators, and I/O devices in automation environments.[1] It facilitates direct connections among these components, enabling seamless integration within industrial systems.[1] The primary purpose of DeviceNet is to support low-level device-to-device communication, allowing for efficient data exchange, control signals, and real-time monitoring in manufacturing and process control applications.[1] Built on the Controller Area Network (CAN) technology for its lower layers and the Common Industrial Protocol (CIP) for upper layers, it allows both power and data to be transmitted over a single cable, simplifying wiring and reducing installation complexity.[1] DeviceNet targets factory automation settings where cost-effective and rugged networking solutions are essential for integrating simple I/O points and devices.[1] Originally developed by Allen-Bradley and publicly released in 1994, then transferred to and managed by the Open DeviceNet Vendors Association (ODVA) in 1995, it draws from proven automotive networking principles to ensure reliability in harsh industrial conditions.[1][3][2]Key Features
DeviceNet supports both master-slave and peer-to-peer communication modes, enabling flexible control architectures where a master device can poll slaves for data or devices can exchange information directly.[2][5] This dual-mode capability allows for efficient integration of simple I/O devices with more complex networked systems in industrial settings.[2] The protocol employs a trunkline-dropline topology, which facilitates flexible wiring arrangements suitable for harsh industrial environments by allowing devices to tap into a main trunk line via drop lines.[2][6] Additionally, DeviceNet integrates power and data transmission over a single cable, typically providing 24 V DC power alongside communication signals, which simplifies installation and reduces wiring complexity compared to separate power and signal lines.[2][5] For real-time control, DeviceNet ensures deterministic behavior through cyclic (implicit) messaging, such as polled or strobed exchanges for periodic I/O updates, and acyclic (explicit) messaging for on-demand data transfers.[2][5] As an open standard managed by the Open DeviceNet Vendors Association (ODVA), it promotes interoperability among devices from multiple vendors by adhering to common specifications.[2] The network scales to support up to 64 nodes while leveraging low-cost, off-the-shelf components based on Controller Area Network (CAN) technology for reliable operation.[2][5]History
Development Origins
DeviceNet originated in the early 1990s from Allen-Bradley, now part of Rockwell Automation, as a response to the growing complexity and cost of wiring in industrial automation systems.[3][7] In 1992, the company began developing the protocol and sharing details with partners to foster collaboration.[3] This initiative aimed to simplify connections between programmable logic controllers (PLCs) and field devices, such as sensors and actuators, by leveraging emerging network technologies.[7] The protocol was built on the Controller Area Network (CAN) technology, originally developed by Robert Bosch GmbH in the 1980s for automotive applications to replace bulky wiring harnesses with efficient serial communication.[8][7] Allen-Bradley adapted CAN's robust physical layer for industrial use, enabling DeviceNet as a device-level network. The initial design goals focused on facilitating bidirectional data transfer between controllers and field devices over a single cable, thereby eliminating traditional point-to-point wiring schemes that were labor-intensive and prone to errors.[7] This approach promised reduced installation costs—up to three to four times lower—and improved system flexibility.[7] DeviceNet made its first public appearance at the Industrial Computer Expo (ICEE) show in Chicago in March 1994, marking its debut as an open, low-cost network solution.[3][9] In 1995, Allen-Bradley transferred stewardship of the technology to the newly formed Open DeviceNet Vendor Association (ODVA), a nonprofit organization founded to promote multi-vendor interoperability and standardization.[3][2] This move accelerated adoption by encouraging broader industry participation. Following its release, DeviceNet saw rapid early adoption in manufacturing applications during the mid-1990s, particularly for connecting simple I/O devices in assembly lines and process control.[2] By the late 1990s, the network's installed base had grown to millions of nodes worldwide, demonstrating its impact on reducing wiring complexity and enhancing diagnostics in industrial environments.[2]Standardization and Evolution
DeviceNet was formally declared an official standard by the Open DeviceNet Vendors Association (ODVA) in 1999, marking its integration into the broader Common Industrial Protocol (CIP) family alongside ControlNet and the emerging EtherNet/IP. This standardization effort, managed by ODVA since its founding in 1995, ensured DeviceNet's media-independent upper layers aligned with CIP's object-oriented architecture for control, configuration, and diagnostics, promoting interoperability across industrial networks.[10] In 2000, DeviceNet achieved international recognition through its adoption as IEC 62026-3, which specifies the interface for low-level actuator and sensor networks in low-voltage switchgear and controlgear applications. This standard, published by the International Electrotechnical Commission, defined the protocol's physical and data link layers for global use, facilitating cross-vendor compatibility in industrial settings.[11] ODVA has driven DeviceNet's evolution through ongoing specification updates, incorporating standardized device profiles to define consistent object implementations for various equipment types, such as drives and I/O modules. Safety extensions via CIP Safety, introduced in 2005, enabled fail-safe communications for applications like safety I/O blocks and light curtains, while conformance testing programs ensure vendor products meet protocol requirements through independent verification.[12][13] During the 2000s, key enhancements included better integration with higher-level CIP networks like EtherNet/IP for hierarchical system designs.[2] ODVA maintains backward compatibility in specification revisions to protect existing installations, while certifying vendors through Declarations of Conformity; by the 2010s, the organization had grown to over 240 member companies, and as of 2025, it includes over 400 members, fostering widespread adoption and innovation in DeviceNet technology.[7][14]Architecture
Physical Layer
DeviceNet employs a trunkline-dropline topology, where a main trunk cable connects to drop lines branching off to individual devices, enabling flexible industrial network layouts. This topology supports both round and flat cables, with thick round cables typically used for the trunkline due to their robustness, and thin round or flat cables for shorter drop connections. The design facilitates easy expansion and maintenance in harsh manufacturing environments.[15] The network supports three data rates: 125 kbit/s, 250 kbit/s, and 500 kbit/s, each with corresponding maximum trunkline lengths to ensure signal integrity over distance. For thick round cable, the maximum lengths are 500 m at 125 kbit/s, 250 m at 250 kbit/s, and 100 m at 500 kbit/s; flat cable allows up to 420 m at 125 kbit/s, 200 m at 250 kbit/s, and 75 m at 500 kbit/s. Drop lines are limited to 6 m per connection, with cumulative drop lengths capped at 156 m for 125 kbit/s, 78 m for 250 kbit/s, and 39 m for 500 kbit/s to minimize signal degradation.[15][2] Cable construction features a twisted-pair configuration for both power and data transmission: a red/black pair for power and a blue/white pair for signal in round cables, with an uninsulated drain wire for grounding in round types, while flat cables omit the drain wire. Signal pairs use 24 AWG conductors in thin round cables, providing flexibility for drops, whereas thick round cables employ 18 AWG for signals to handle longer runs. These cables operate at 24 V DC and support up to 8 A current delivery in Class 1 configurations for thick round and flat types, enabling integrated power distribution to devices without separate wiring.[15] Connectors adhere to sealed 5-pin mini or micro-style formats, offering IP67-rated protection against dust and water ingress, ideal for wet or oily industrial settings. These connectors ensure reliable mating on the trunk and drops, with options for screw-terminal styles in less demanding IP20 environments.[2][15] Power supply integration uses power taps to distribute 24 V DC from centralized supplies with overcurrent protection, with per-drop current limits based on drop length to ensure voltage drop remains below 0.35 V (e.g., max approximately 750 mA at 6 m using the formula I = 4.57 / L in meters). Segmentation via power taps isolates faults, preventing network-wide disruptions by dividing the trunk into independent sections, each with its own supply if needed.[15] To prevent signal reflections, the network requires 120 Ω termination resistors at both trunk ends, connected across the blue and white signal wires, maintaining characteristic impedance throughout the medium. DeviceNet's physical layer utilizes differential signaling derived from the Controller Area Network (CAN) standard for robust transmission in noisy environments.[15][2]Data Link Layer
The data link layer of DeviceNet provides the mechanisms for reliable frame transmission and medium access control (MAC) in a multi-node industrial network, ensuring deterministic and fault-tolerant communication among devices. It is based on the Controller Area Network (CAN) protocol, utilizing standard, unmodified CAN compliant with ISO 11898-1 for physical signaling and MAC functions.[2][4] This layer handles the transfer of data frames between nodes without higher-level addressing, focusing on low-level protocol logic to support real-time performance. DeviceNet employs CAN 2.0A in Classical CAN (CAN CC) mode, which uses 11-bit identifiers exclusively and prohibits remote frames to simplify operations and avoid unnecessary requests for data transmission.[2][4] Medium access is managed through non-destructive bitwise arbitration, where multiple nodes can attempt to transmit simultaneously; the node with the lowest identifier value (priority determined bit-by-bit, with dominant bits overriding recessive ones) gains control without collisions or data loss.[16][2] This arbitration process ensures efficient bus utilization in environments with up to 64 nodes. The CAN frame structure in DeviceNet consists of the following fields for data transmission:| Field | Description | Length |
|---|---|---|
| Start of Frame (SOF) | Single dominant bit to synchronize nodes and indicate frame beginning. | 1 bit |
| Arbitration Field | 11-bit identifier (for priority) + Remote Transmission Request (RTR) bit (dominant for data frames). | 12 bits |
| Control Field | 6 bits: 4-bit Data Length Code (DLC) specifying 0-8 bytes of data, plus 2 reserved bits (set dominant). | 6 bits |
| Data Field | Variable payload carrying application data, transmitted most significant byte first. | 0-64 bits (0-8 bytes) |
| Cyclic Redundancy Check (CRC) | 15-bit checksum for error detection, followed by a recessive delimiter bit. | 16 bits |
| Acknowledge (ACK) | 2 bits: Recessive slot for ACK (dominant by at least one receiver) + recessive delimiter. | 2 bits |
| End of Frame (EOF) | 7 recessive bits to signal frame completion. | 7 bits |