CAN

About CAN

The CAN bus (Controller Area Network) is an asynchronous, serial fieldbus system. In 1983, Bosch developed the CAN bus for networking control units in automobiles. The goal of this development was to reduce cable lengths and weight. In 1987, the first version of a functional CAN bus was unveiled in collaboration with Intel.

Since then, CAN has been standardized internationally as ISO 11898 and defines Layer 1 (Physical Layer) and Layer 2 (Data Link Layer) in the OSI reference model. The Physical Layer can be implemented in two variants: High-Speed CAN (according to ISO 11898-2) and Low-Speed CAN (ISO 11898-3).

CAN Data Link Layer

CAN is a multi-master bus system with multidrop capabilities. Messages are transmitted, and any node in the network can receive a message from another node; this process is called bit-by-bit arbitration.

In addition to automotive engineering, CAN is now used in all types of transportation systems, as well as in machine control, home and building automation, mobile machinery, and medical devices.

The reliability of these protocols is very high due to standardization. Failures can be identified and verified with a very high degree of certainty.

CAN Physical Layer

Thanks to the use of twisted-pair cable and short patch cables, CAN is one of the most robust networking technologies.

The most commonly used physical layer is High-Speed CAN, which supports data rates of up to 1 Mbit/s.

In contrast, Low-Speed CAN is a fault-tolerant, low-power transmission protocol. Transmission in this variant is limited to 125 kbit/s and is therefore rarely used.

Standardized high-layer protocols

CANopen

CANopen is a CAN-based Layer 7 (application layer) communication protocol. Devices are connected to the CANopen network via 9-pin D-Sub connectors. A maximum of 127 devices can be connected to a CANopen network. The data transfer rate of a CANopen network depends on the bus length.