CAN-FD
CAN with Flexible Data-Rate.

CAN with Flexible Data-Rate is defined by ISO 11898-1:2015. It is a fully backward-compatible extension of classical CAN designed to address two limitations of the original protocol: the 8-byte payload limit and the bus-wide arbitration rate ceiling.

The bus uses two differential signals — CAN_H and CAN_L — typically on a twisted pair terminated at both ends with 120 Ω. The same physical layer carries both classical CAN and CAN-FD traffic; CAN-FD frames are distinguished by the FDF bit and a different inter-frame structure.

Each CAN-FD frame can carry up to 64 bytes of data (vs. 8 in classical CAN). The frame is split into an arbitration phase (run at the classical CAN bitrate to preserve multi-node arbitration) and a data phase (run at a higher rate once the transmitter has won the bus). Typical data-phase rates range from 2 to 8 Mbps depending on transceiver and topology.

CAN-FD is heavily used in automotive ECU networks, industrial machine control, and increasingly in robotics and battery-management systems where higher per-message payloads reduce protocol overhead.