CAN bus

CAN bus
Name	Controller Area Network
Abbreviation	CAN
Designed by	Robert Bosch GmbH
Initial release	1986
Bus type	Serial communication
Topology	Multi-master
Max nodes	112
Related	ISO 11898, SAE J1939

CAN bus

The Controller Area Network is a serial multi-master communication system developed for robust in-vehicle networking. Originating at Robert Bosch GmbH and standardized in ISO 11898, it underpins modern Bosch Rexroth-derived automotive architectures and influences industrial protocols such as DeviceNet and SAE J1939. Prominent manufacturers and organizations including Bosch, NXP Semiconductors, Infineon Technologies, Texas Instruments, and Vector Informatik provide silicon and tools supporting the ecosystem.

Overview

CAN emerged to replace point-to-point wiring used in Mercedes-Benz and BMW platforms, reducing weight and complexity for models like those from Volkswagen and Audi. The technology matured alongside standards bodies such as International Organization for Standardization and consortia like AUTOSAR, facilitating adoption across suppliers including Continental AG and Denso Corporation. Early research and demonstrations involved contributors from Telefunken and semiconductor groups within Philips. CAN’s multi-master arbitration and event-driven messaging made it appealing for control systems in Daimler Truck and embedded subsystems in Rolls-Royce Motor Cars designs.

Technical Specifications and Protocols

The canonical specification suite is published under ISO 11898 and extended by profiles like SAE J1939, ISO 15765-4 (diagnostics via CAN), and industrial derivatives such as CANopen from the CiA (CAN in Automation) organization. Implementations use two primary frame formats: the original 11-bit identifier standard frame and the extended 29-bit identifier format adopted by heavy-duty networks in Volvo Group vehicles. Error handling mechanisms reference models used in IEC 61508 functional safety guidance. Silicon implementations by NXP Semiconductors and Microchip Technology expose MAC and physical interface features compliant with ISO 11898-1 and ISO 11898-2.

Physical Layer and Wiring

The physical medium conforms to variants in ISO 11898-2 (high-speed twisted pair) and ISO 11898-3 (fault-tolerant medium). Typical wiring harnesses in Ford Motor Company and General Motors vehicles use shielded or unshielded twisted pair with termination resistors to match characteristic impedance. Connectors and pinouts are often specified by OEMs and suppliers such as TE Connectivity and Molex, while diagnostic access via OBD-II ports ties to standards like ISO 9141-2 and SAE J1962. In industrial automation, implementations may integrate with fieldbus gateways produced by Siemens and Schneider Electric, adapting to environmental standards from IEC committees.

Message Framing and Arbitration

CAN frames carry control, identifier, data, CRC, and acknowledgement fields. The arbitration process is non-destructive, allowing highest-priority identifiers to dominate bus access; this behavior has been studied in contexts like IEEE 802.3 competition models and applied in Bosch-led control strategies. Frame types include data frames, remote frames, error frames, and overload frames, with bit-stuffing rules defined in ISO 11898-1. Higher-layer protocols such as ISO 15765-2 (transport protocol) segment larger payloads into multiple CAN frames for diagnostics used by BMW and Mercedes-Benz service tools. Stack vendors including Vector Informatik, Kvaser, and PEAK-System provide APIs aligning with these framing rules.

Applications and Implementations

CAN is ubiquitous in passenger vehicles from Toyota Motor Corporation, Honda Motor Co., Hyundai Motor Group, and Nissan Motor Co. for engine management, body control modules, and infotainment gateways. Heavy-duty applications include fleets by Volvo Group, Daimler Truck, and MAN SE using SAE J1939 for powertrain data. Aerospace and defense uses by contractors such as Airbus and Lockheed Martin explore adapted CAN variants under avionics standards. Industrial automation deployments involve Rockwell Automation and Beckhoff integrating CANopen for motion control; maritime systems from Kongsberg and Rolls-Royce plc use CAN-based networks for sensor and actuator communication.

Reliability, Security, and Standards Compliance

CAN’s deterministic arbitration and retransmission improve reliability in safety-critical domains guided by ISO 26262 functional safety assessments adopted by Volkswagen Group and Renault Group. However, security weaknesses exposed in research by teams at University of California, San Diego and industry reports from IOActive prompted secure gateway designs from Bosch and secure boot measures by NXP Semiconductors. Compliance testing follows conformance suites from CiA and certification efforts involving TÜV Rheinland and SGS-TÜV Saar. Extensions like CAN-FD increase payload capacity and require updates to timing analyses used in SAE guidance and IEC risk assessments.

Category:Computer buses