Data Communication in the Automobile – Part 2: Reliable Data Exchange with CAN

physical bus connection, data rates, and the voltage levels on both CAN wires. CAN uses differential signal transmission, which reduces noise sensitivity and requires two communication wires (CAN high and CAN low) that are terminated at both ends with characteristic impedance RT of 120 Ω. CAN high-speed is mainly used in drive and chassis applications. It is primarily implemented by the CAN high-speed transceiver, which supports a maximum data rate of 1 Mbit/s. The CAN low-speed physical layer has been used mainly in the convenience area. It is placed in doors, seats, As presented in part 1 of our article series, the increasingly complex electronic systems in automobiles are calling for a higher level of data exchange between the ECUs. In order to ensure this with sufficient reliability and speed, the CAN bus was developed. CAN stands for Controller Area Network. As the name implies, the CAN bus can link a larger area and reach a length up to multiple kilometers. The CAN bus was developed by Bosch [1] and became a standard in 1993. It is currently available as ISO 11898 (Figure 1). The standard is divided into multiple parts. The first part specifies the CAN protocol and covers all aspects of the data link layer (framing, addressing, bus access, data integrity) and the physical signal coding as part of the physical layer of the ISO 7498 reference model – the socalled OSI layer model (OSI: Open Systems Interconnection). The CAN controller was developed for handling the CAN protocol. Parts 2 and 3 of ISO 11898 describe two versions of the physical layer, namely CAN high-speed and CAN low-speed. The latter is also often called fault-tolerant CAN because it continues functioning if one of its two wires breaks, although with diminished reliability. Parts 2 and 3 also cover the physical layer of the ISO reference model, including the Data Communication in the Automobile – Part 2: Reliable Data Exchange with CAN