Terminology » CAN-FD: Advantages and Disadvantages Overview

CAN-FD: Advantages and Disadvantages Overview

automotive can-fd can-fd protocol

Introduction : Classical CAN published earlier had limitations of substantial overhead due to use of only 8 data bytes and speed of about 1 Mbps. CAN-FD overcomes the primary limitations of the original CAN 2.0 protocol while maintaining a high degree of backward compatibility.

What is CAN-FD?

CAN-FD (Controller Area Network - Flexible Data Rate) is an enhanced version of the classic CAN protocol widely used in automotive and industrial applications. It enables higher data rates, increased payload capacity and improved network performance.

Once a node has won arbitration and begins transmitting the data payload, the protocol switches to a significantly higher data rate (typically up to 5 Mbit/s, with some implementations reaching 8 Mbit/s or higher). This “flexible data rate” is what gives the protocol its name and its primary advantage.

Following are the features of CAN-FD protocol.

  • CAN-FD frame payload : 64 bytes
  • CAN-FD frame speed (maximum) : 8 Mbps
  • Same usage as with CAN 2.0
  • CAN Frame identifier size : Two message formats base frame with 11 bits and extended frame with 29 bits
  • CRC size : 17-bit (for payload of up to 16 bytes) or 21 bit (payloads larger than 16 bytes)
  • References : ISO 11898-1, ISO 11898-2, ISO 11898-5

Advantages of CAN-FD

Following are some of the benefits of CAN-FD.

  1. It offers substantial increase in data throughput. By allowing for a higher bit rate during the data phase, CAN-FD can transmit data significantly faster than classical CAN. In practice, data rates up to 5 Mbps are achievable. This is very useful for applications such as advanced driver assistance systems (ADAS), modern infotainment systems and complex industrial control loops.
  2. It can transmit up to 64 bytes of data in a single frame, an eightfold increase over the 8 byte limit of classical CAN. This larger data payload improves network efficiency.
  3. As mentioned, higher data rate and larger payload size can help in reducing latency required for critical communications. This leads to more efficient use of bus.
  4. CAN-FD is designed to be largely compatible with existing CAN 2.0 networks.
  5. CAN-FD retains the proven and reliable arbitration and error detection mechanisms of the original CAN protocol. This ensures that it remains robust standard for safety applications.

Disadvantages of CAN-FD

Following are some of the limitations of CAN-FD.

  1. CAN-FD requires specific transceivers that are designed to handle the faster bit speeds and ensure signal integrity.
  2. Due to use of higher data rate. there is potential for signal reflections and ringing, which can introduce errors. Hence CAN-FD requires careful design and analysis of physical network layout compared to lower speed classical CAN.
  3. Like the original CAN protocol, CAN-FD does not include any built-in security features such as encryption or authentication. Hence it is vulnerable to security threats like spoofing or denial of service attacks. To secure CAN-FD, it requires implementation of higher level security protocols or use of dedicated security hardware.
  4. The dual bit rate and the need for more precise network design add a layer of complexity to implementing and troubleshooting CAN-FD networks compared to classical CAN.

Conclusion: CAN-FD significantly boosts speed and flexibility compared to traditional CAN, making it ideal for modern ECUs and complex network architectures