CAN XL Technology Introduction

The Next Evolution of CAN Communication

For more than thirty years, the Controller Area Network (CAN) has been the backbone of communication in vehicles and many industrial applications. Starting with CAN Classic, which established a robust and cost-effective bus system, the technology was later extended with CAN FD to allow faster data transmission and significantly larger payloads. Now, with CAN XL, the third generation of the protocol has arrived. Building on the same physical foundation, it introduces decisive improvements in data rate, payload size, and integration flexibility, bringing CAN into the era of zonal architectures and IP-based communication.

From CAN Classic to CAN XL

The development of CAN has always been driven by increasing demands for bandwidth and efficiency. CAN Classic offered up to 1 Mbit/s and eight data bytes per frame, which was sufficient for many years. CAN FD extended this to 64 data bytes and enabled flexible switching of bit rates within the data phase, reaching up to 8 Mbit/s. CAN XL now continues this path by supporting payloads of up to 2,048 bytes per frame and data rates of up to 20 Mbit/s when operating in its fast mode. With these capabilities, CAN XL not only surpasses its predecessors but also positions itself as a bridge technology between traditional fieldbuses and high-speed Ethernet networks.

Structure and Frame Format

At the core of CAN XL is the XL Frame Format (XLFF), which extends the familiar CAN frame structure. One of the most important innovations is the separation of the identifier into two parts. The Priority Identifier with a length of eleven bits is used for arbitration, while the Acceptance Field with 32 bits serves as a flexible addressing and filtering mechanism. This separation allows messages to be prioritized and routed more efficiently.

The frame structure also introduces additional fields that expand the protocol’s versatility. The Service Data Unit Type (SDT) defines which higher-layer protocol is being transported, enabling tunneling of CAN FD or the transmission of IP packets. The Virtual CAN Network ID (VCID) makes it possible to run up to 256 logical networks on a single physical segment, comparable to VLANs in Ethernet. Another addition is the Simple Extended Content (SEC) bit, which indicates whether further headers, such as for encryption or fragmentation, are included. Together, these features allow CAN XL to serve as a highly adaptable platform that supports both legacy applications and modern data-driven architectures.

CAN XL frame format

Data Integrity and Reliability

As data fields become larger, ensuring reliability becomes even more critical. CAN XL introduces two cyclic redundancy check fields to safeguard transmissions: the Preface CRC protects the control information, while the Frame CRC secures the entire frame. This cascaded approach achieves a Hamming distance of six, meaning that up to five randomly distributed bit errors can be reliably detected. Such robustness is vital when transporting large payloads or safety-relevant data in automotive and industrial environments.

Physical Layer and Mode Switching

One of the strengths of CAN XL lies in its ability to reuse the existing physical infrastructure. Like its predecessors, it is based on a two-wire twisted-pair bus with 120-ohm termination. This means that in many cases, existing cabling can be retained, making migration easier.

The typical CAN XL cabling

To achieve higher data rates beyond 8 Mbit/s, CAN XL introduces the concept of mode switching in combination with new SIC XL transceivers. In the arbitration phase, communication still follows the conventional scheme, but for the data phase, the system can switch into a fast push-pull mode with reduced signal amplitude. This allows bit rates of up to 20 Mbit/s while maintaining the reliability of the CAN transmission principle. Although classical error frames are limited in this fast mode, reliability is ensured by the enhanced CRC mechanisms.

Mode switching enables high data rates with high robustness. Additional fields in the CAN XL frame provide structured meta-information for processing in higher protocol layers.

Advanced Features

Beyond speed and payload, CAN XL introduces optional enhancements that prepare the protocol for future challenges. One of these is CANsec, a security extension designed to protect against cyber-attacks. It embeds authentication data directly into the frame and secures the communication channel without requiring higher-layer security solutions. Another optional mechanism is frame fragmentation, which allows very large frames to be interrupted so that high-priority control messages can pass through without losing the integrity of the larger transmission. Additionally, the protocol supports pulse-width modulation coding as an alternative to the traditional NRZ method, further extending the possible bit rates depending on the network design.

Standardization and Ecosystem

CAN XL has been officially standardized in ISO 11898-1:2024. Complementary specifications, guidelines, and recommendations are developed by CAN in Automation (CiA), covering aspects such as test plans, higher-layer services, application notes, and add-on security concepts. This ensures a solid foundation for the technology and gives manufacturers and suppliers a clear framework for implementation.

Advantages and Challenges

The key advantages of CAN XL lie in its combination of high data capacity and backward compatibility. With up to 2,048 bytes per frame, not only sensor data but also IP packets can be transmitted efficiently. At the same time, existing CAN infrastructures can be utilized, enabling mixed environments with Classic, FD, and XL. Particularly valuable for the future is the ability to create virtual networks with VCID and thus implement zonal architectures that allow load balancing and targeted quality assurance of data traffic.

However, this expanded functionality also presents challenges. The complexity of protocol evaluation increases, and for high bit rates above 8 Mbps, mode switching is necessary, which limits traditional mechanisms such as error frames. The communication standard for CAN XL (ISO 11898-1:2024) has been specified, so OEMs and suppliers can now begin practical implementation and integration into existing architectures.

CAN XL in Comparison with Automotive Ethernet

It is tempting to compare CAN XL directly with Automotive Ethernet, since both are candidates for high-performance in-vehicle networking. Ethernet achieves much higher data rates, up to 10 Gbit/s, and is therefore the preferred choice for bandwidth-intensive applications such as infotainment or backbone connections. CAN XL, on the other hand, offers payloads of up to 2,048 bytes – more than the standard Ethernet MTU of 1,500 bytes – and excels in deterministic and cost-sensitive environments. While Ethernet typically requires star or ring topologies, CAN XL continues to operate on simple line structures, which helps reduce cabling complexity. Rather than competing directly, both technologies complement each other: Ethernet for ultra-high-bandwidth domains, CAN XL for zonal architectures, sensor data aggregation, and seamless integration with legacy CAN networks.

Applications and Outlook

The main application field of CAN XL is in zonal vehicle architectures, where electronic control units within a functional zone communicate locally and forward aggregated data to central processors. This approach reduces wiring effort, supports modular designs, and fits perfectly with the flexibility of CAN XL. Another key use case is the efficient transmission of large sensor data streams, for example in advanced driver assistance systems, where many signals need to be combined and processed. Beyond the automotive sector, CAN XL is also suitable for industrial automation, serving as a robust backbone or sub-backbone network technology.

With toolmakers and hardware vendors already offering starter bundles that combine interfaces, transceivers, and software APIs, developers today can begin exploring the practical benefits of CAN XL. This lowers the barrier to entry and accelerates the path from research into real-world applications.