Data Link (ISO 11898-1:2015)
CAN-FD
CAN with Flexible Data-rate — 8× the payload, faster data phase.
Bitrate
Up to 5 Mbit/s in data phase
Topology
Same physical layer as classical CAN
Introduced
2012
Overview
CAN-FD extends classical CAN with up to 64 bytes of payload and a higher bit rate during the data phase. The arbitration phase remains compatible, allowing gradual migration of existing bus topologies.
Frame format
| Field | Bits | Description |
|---|---|---|
| SOF | 1 | Start of Frame |
| Identifier | 11 / 29 | Arbitration ID |
| FDF | 1 | Flexible Data-rate Format flag |
| BRS | 1 | Bit Rate Switch — enables fast data phase |
| ESI | 1 | Error State Indicator |
| DLC | 4 | Data length code (0–15 mapped to 0–64 bytes) |
| Data | 0–512 | Up to 64 bytes of payload |
| CRC | 17 / 21 | Stronger CRC than classical CAN |
Byte structure — request & response
CAN-FD — ISO 11898-1:2015
Frame template
[SOF][ID:11/29b][FDF:1b][BRS:1b][ESI:1b][DLC:4b][Data:0–64B][CRC:17/21b][ACK]Request
| Off | Size | Field | Value | Description |
|---|---|---|---|---|
| 0 | 11/29 bit | Arbitration ID | 0x18EAFF00 | Standard or extended ID. |
| — | 1 bit | FDF | 1 | Marks frame as CAN-FD. |
| — | 1 bit | BRS | 1 | Switch to fast bit rate for data phase. |
| — | 1 bit | ESI | 0 | 0 = error-active node, 1 = error-passive. |
| — | 4 bit | DLC | 0xF | 0–8 = bytes; 9–15 mapped to 12,16,20,24,32,48,64. |
| 0…63 | 0–64 B | Data | 01 02 … 40 | Payload up to 64 bytes. |
| — | 17/21 bit | CRC | auto | Stronger CRC than classical CAN. |
Response
| Off | Size | Field | Value | Description |
|---|---|---|---|---|
| 0 | 11/29 bit | Arbitration ID | 0x18EBFF00 | Reply ID per application protocol. |
| — | 4 bit | DLC | 0xA | DLC=0xA → 24 bytes. |
| 0…23 | 24 B | Data | 62 F1 90 … | E.g. UDS positive response over CAN-FD. |
CAN-FD increases payload to 64 B and lets the data phase run at up to 5 Mbit/s while keeping arbitration compatible with classical CAN.
Use cases
- · ECU flashing
- · ADAS sensor fusion
- · High-bandwidth body control
Pros
- 64-byte payload
- Faster data phase
- Backward-compatible physical layer
Cons
- Requires CAN-FD capable controllers
- More complex bit timing
Request / Response examples
Bulk telemetry frame
Request
ID:0x123DLC:15(64B)Data:32bytesofsensorblock...
Response
(broadcastframe)
Single CAN-FD frame replaces eight classical CAN frames for one ADAS snapshot.