{"id":"can-fd","model_id":"CAN FD","name":"CAN FD","summary":"CAN FD is a CAN data link layer protocol that increases bit rate and payload size. It can transmit data faster than 1 Mbit/s and carries a data field of up to 64 bytes instead of 8 bytes. It uses the FDF bit to distinguish FD frames and the BRS bit to switch to the higher bit rate during the data phase.","study_notes":["Robert Bosch GmbH started CAN FD development in 2011 in cooperation with carmakers and other CAN experts.","CAN FD overcomes two CAN CC limits: data rates above 1 Mbit/s and a payload up to 64 bytes instead of 8 bytes.","A 1:8 ratio between arbitration-phase and data-phase bit rates gives approximately six times higher throughput, accounting for extra header and CRC bits.","The FDF bit distinguishes CAN FD data frames from CAN CC data or remote frames: recessive means CAN FD, dominant means CAN CC.","The BRS bit applies the second bit rate when recessive; when dominant, the arbitration-phase bit time setting is used in the data phase.","The ESI bit reports error status: dominant indicates error active, recessive indicates error passive.","CAN FD data frames with 11-bit identifiers use FD base frame format (FBFF); those with 29-bit identifiers use FD extended frame format (FEFF).","CAN FD does not support remotely requested data frames.","The CAN FD protocol controller also supports CAN CC frames.","CAN CC and CAN FD are standardized together in ISO 11898-1:2024.","The control field includes FDF, BRS, ESI and DLC bits in addition to CAN CC control bits."],"safety_notes":["The CRC field uses 17-bit polynomials for payloads up to 16 bytes and 21-bit polynomials for frames larger than 16 bytes, plus an 8-bit stuff-bit counter and a parity bit.","The document states these safeguards guarantee all single failures are detected under all conditions and improve multiple-failure detection.","Non-ISO CAN FD controllers are not compliant with ISO 11898-1 and do not implement the additional safeguard features."],"sources":[{"url":"https://www.can-cia.org/can-knowledge/can-fd-the-basic-idea","title":"CAN FD","accessed":"2026-10-25"}],"verification":{"status":"source_checked","checked_at":"2026-10-25","values":3,"method":"llm_source_check"},"updated_at":"2026-10-25","type":"protocol","spec":{"transports":["other"],"architecture":"producer_consumer","encoding":"binary","default_ports":[],"data_types":[],"standard_body":"ISO","standard_ref":"ISO 11898-1:2024","related":[]},"url":"https://machineschema.com/protocol/can-fd","license":"https://creativecommons.org/licenses/by/4.0/"}