The Next Advancement of CAN Communications

How does CAN, a 30-year-old serial communication standard that allows microcontrollers, sensors and electronic control units to communicate with each other without a central host computer stay on top?

By getting better, of course.

CAN XL (controller area network extended data-field length) is the third-generation CAN communication protocol. CAN in Automation (CiA) is the international users’ and manufacturers’ group for CAN, internationally standardized in the ISO 11898 series. Starting with the CAN Classic bus system, the technology was later extended with CAN FD to allow faster data transmission and significantly larger payloads.

CAN Classic offered up to 1 Mbit/sec 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/sec. CAN XL continues this by supporting payloads of up to 2,048 bytes per frame and data rates of up to 20 Mbit/sec when operating in its fast mode.

Building on the same physical foundation, CAN XL brings CAN into the era of zonal architectures and IP-based communications. Up to 32 times more data can now be transmitted through a single CAN XL frame compared to a CAN FD frame.

Humanoid and autonomous mobile robots are generating more data for motion control, sensor fusion, diagnostics and software than traditional controller area network technologies were designed to support.

In response, CAN XL aims to bridge the gap between traditional CAN networks and automotive Ethernet. Many applications don't need the bandwidth, architecture or added complexity of Ethernet. CAN XL extends CAN-based networking for systems that need more bandwidth than CAN FD can provide without requiring a move to Ethernet. 

Data Integrity and Reliability

Up to five randomly distributed bit errors can be reliably detected in CAN XL. Such robustness is vital when transporting large payloads or safety-relevant data in automotive and industrial environments.

CAN XL solutions are backward-compatible. CAN XL controllers can be integrated into existing CAN FD networks, allowing for easy system upgrades rather than a complete architectural overhaul.

Additionally, there are optional configuration features such as switching off the error signaling and enabling pulse-width modulation (PWM) coding at the attachment unit interface (AUI) as an alternative to the non-return-to-zero (NRZ) coding of CAN. NRZ coding directly maps binary data streams to physical bus levels. NRZ is a binary line-coding scheme in which the signal level stays constant (high or low) for the entire duration of a bit period without returning to a neutral or rest state.

CAN XL is intended for backbone and sub-backbone network applications. It is designed for an easy integration into transmission control protocol and internet protocol (TCP/IP) network systems.

Like its predecessors, CAN XL 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.                                                               

CAN XL can connect seamlessly to CAN networks or to an Ethernet backbone, supporting the trend towards software-defined vehicles.

Key Technical Specifications

• Reliability and security: A dual cyclic redundancy check (CRC) error-detection scheme is employed using a 13-bit PCRC (preamble cyclic redundancy check) and a 32-bit FCRC (frame cyclic redundancy check), supporting core functional safety features.
• Physical layer: Operates over standard 120-ohm twisted-pair cabling and maintains backward compatibility with Classical CAN, CAN FD, and CAN SIC networks.
• Over-the-air updates and diagnostics: Accommodates large data blocks and firmware with reduced overhead and bus utilization.

Beyond speed and payload, CAN XL introduces optional enhancements. One of these is CANsec, a security extension designed to protect against cyberattacks. It embeds authentication data directly into the frame and secures the communication channel without requiring higher-layer security solutions.

CAN XL Won't Replace CAN FD or Ethernet

Rather than competing directly, these technologies complement each other: Ethernet for ultra-high-bandwidth domains and CAN XL for zonal architectures, sensor data aggregation and seamless integration with legacy CAN networks.

Ethernet typically requires point-to-point switched star topologies, while CAN XL maintains the traditional bus topology. This drastically reduces cabling weight, connector complexity and overall cost.

Ethernet achieves much higher data rates – up to 10 Gbit/sec – 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.

In an application such as a humanoid robot hand that would previously require two separate networks for control and high-bandwidth traffic, CAN XL can carry both types on the same bus.

In future, CAN FD, CAN XL and Ethernet will work together in the same designs. CAN FD will remain important for cost-sensitive control networks, while CAN XL will support applications that exceed the practical capabilities of CAN FD. Ethernet will continue to provide the high-speed backbone for systems with much greater bandwidth-intensive systems.