Understanding CAN XL Protocol in Automotive Networks

CAN XL stands for Controller Area Network eXtra Large. It’s a protocol built upon the foundations of classical CAN and CAN FD (CAN with Flexible Data-Rate). Think of it as the third generation of CAN, designed to meet the evolving demands of electrical/electronic (E/E) architectures in modern vehicles.

The primary goal behind developing CAN XL was to bridge the speed gap between the older CAN/CAN FD and the faster Ethernet 100Base-T1. Here’s a breakdown of its key features:

• High Speed: Supports transfer rates of up to 20 Mbps.
• Cost-Effective and Robust: Like its predecessors, it’s designed to be affordable, reliable, and capable of real-time communication.
• Ethernet Tunneling: Allows the transportation of Ethernet frames, enabling a service-oriented architecture for CAN XL nodes.
• Large Data Payload: Supports data field lengths from 1 to 2048 bytes.
• 11-bit Identifiers: Uses 11-bit identifiers, unlike the variable options in older CAN versions.
• CSMA/CR: Employs Carrier Sense Multiple Access/Collision Resolution for managing network traffic.
• Priority Concept: Ensures that more important frames are transmitted without delays through a clear priority system.
• New Fields and Functions: CAN XL is distinct from CAN/CAN-FD, introducing new fields and functions like acceptance field, SDU type, VCAN ID, bit stuffing, CRC (PCRC of 13 bits and FCRC of 32 bits), and transceiver mode switching. Other fields include SDT, SEC, and VCID.
• Virtual Networks: Supports up to 256 virtual networks within a single CAN XL network segment.
• Fixed Stuff Bits: Uses fixed stuff bits in the data phase.

Benefits and Advantages of CAN XL Protocol

Here’s why CAN XL is gaining traction in the automotive industry:

1. High Transmission Reliability: Achieved through two cascaded CRCs, ensuring data integrity.
2. Transceiver Flexibility: Compatible with all types of transceivers.
3. Backward Compatibility (Expected): Aims to be backward compatible with existing CAN and CAN FD networks, allowing a smoother transition without completely replacing existing systems. This mostly requires software configurations of the embedded microcontroller.
4. Flexibility and Ease of Transition: Easier to switch from classical CAN or CAN-FD to CAN-XL, with simple configuration for different bit rates based on network needs.
5. Improved Clarity and Software Development: The new fields in CAN XL provide more clarity and simplify software development.
6. Higher Transmission Speeds: New physical layer technologies like CAN SIC and CAN SIC XL increase transmission speeds up to 20 Mbps, enabling efficient transfer of large data volumes in real-time.
7. Unified Communication: Supports Ethernet frame tunneling, enabling both real-time and service-oriented communication over the same network.
8. Ethernet Endpoint Capability: CAN XL ECU (Electronic Control Unit) can function as an Ethernet endpoint, which is essential for migrating higher-level protocols.
9. Larger Frame Lengths: Ideal for applications requiring the transmission of significant amounts of data.
10. Time-Sensitive Communication: Suitable for safety-critical and real-time applications, such as autonomous driving and advanced driver-assistance systems (ADAS).
11. Scalability and Adaptability: Designed to evolve with automotive requirements, allowing integration of new features and technologies.
12. Reduced Latency: Minimizes communication latency, vital for real-time decision-making in autonomous vehicles and safety-critical systems.

Conclusion

CAN XL (CAN eXtra Large) offers a compelling package of advantages: higher data rates, extended frame lengths, real-time communication, improved network management, backward compatibility, scalability, reduced latency, and overall reliability and efficiency.

It’s designed to meet the growing demands of advanced automotive systems, especially in the areas of autonomous driving and safety-critical applications. The future of CAN XL looks promising as a forward-thinking communication protocol that caters to the evolving needs of the automotive industry for higher data throughput and time-sensitive communication. Its adoption and standardization are continuously developing in response to the ever-advancing technologies and requirements in the automotive sector.

Refer CAN vs CAN-FD vs CAN-XL for difference between CAN versions.