Acronym · Automotive
CAN FD (CAN with Flexible Data-rate)
An extension of CAN that keeps arbitration at classic speed but switches to a higher bit rate for the data phase and raises the payload from 8 to 64 bytes, increasing throughput without re-wiring the vehicle.
- Also known as
- CANFD
- Type
- Acronym
- Domain
- Automotive, In-vehicle networking
- Also relevant to
- Interfaces & SerDes
Notes
Adopted widely from around 2015, largely because 8-byte classical frames could not carry modern diagnostics or flash updates efficiently.
Overview
CAN FD, short for CAN with Flexible Data-rate, is an extension of the Controller Area Network bus used in vehicles and machines that sends the data part of each frame at a higher bit rate and carries up to 64 bytes per frame instead of 8. It raises throughput on existing CAN wiring while keeping CAN's proven arbitration and error handling. Introduced by Bosch in 2012, it is standardised alongside classic CAN in ISO 11898-1 and is now common in new vehicle networks.
How it works
On a CAN bus, all nodes must stay synchronised while several of them compete to send, which limits classic CAN to 1 Mbit/s. CAN FD keeps this arbitration phase at the classic rate, but once one node has won the bus, nobody else needs to keep up bit by bit, so the transmitter can switch to a faster rate for the data phase. A bit called FDF marks a frame as CAN FD, and a bit-rate-switch (BRS) bit signals that the faster rate applies; the bus switches back to the slower rate before the acknowledgement. The data phase rate is limited mainly by the transceivers and the network layout.
The data field can hold up to 64 bytes, using a new data length coding, and the frame carries a stronger CRC and a stuff-bit counter to keep error detection robust over the longer payload. The CAN in Automation association notes that with a 1 to 8 ratio between arbitration and data rates, throughput rises roughly sixfold once the extra header and CRC bits are counted.
CAN FD controllers also handle classic CAN frames, but a classic-only controller treats a CAN FD frame as an error, so mixed networks need care. CAN XL, a later generation, pushes payloads and rates further.
Examples
- An automotive microcontroller with several CAN FD controllers based on licensed IP such as Bosch's M_CAN module.
- A powertrain or battery management network running a 500 kbit/s arbitration phase and a faster data phase to move 64-byte frames.
- Software updates sent to an ECU over CAN FD, where the larger frames and faster data phase help shorten flashing time.
- A gateway ECU bridging classic CAN, CAN FD and automotive Ethernet segments in one vehicle.
Why it matters
The automotive industry's bandwidth needs outgrew classic CAN, and CAN FD lets carmakers raise capacity on the same kind of wiring without moving every link to Ethernet. Automotive microcontroller and SoC architects must include CAN FD controllers, transceiver and ECU designers handle its timing and signal integrity, and AUTOSAR and driver engineers configure its communication stacks.
Related terms
Part of the Automotive glossary, with every term in the topic and the lifecycles, tools and standards that use them.
Where it appears on the Hub
Used on 5 pages of the Hub. In each group, the pages that mention it most come first.
Standards
Suggest an improvement
Suggest an improvement to this entry
A clearer definition, an example, a correction or a source an editor can check. Editors review every suggestion before the entry changes.
Last reviewed . Written by The Semiconductor Hub editorial team. The full glossary