PROTOCOL · PHYSICAL / DATALINK LAYER · 2015-present
CAN-FD protocol
CAN with Flexible Data-Rate (ISO 11898-1:2015).
What is CAN-FD?
CAN-FD (CAN with Flexible Data-Rate) is the evolution of classical CAN that supports payloads up to 64 bytes per frame (vs 8 bytes on classical CAN) and a faster data-phase bit rate (up to 8 Mbit/s) while keeping the arbitration phase at classical CAN speeds. Standardised in ISO 11898-1:2015. Used on modern Bosch MD1/MG1 ECUs and many BMW G-chassis and Mercedes 2018+ platforms.
Key characteristics
- Same physical layer as classical CAN — same wiring, same termination, same connectors.
- Arbitration phase: 500 kbit/s or 1 Mbit/s (classical-CAN compatible).
- Data phase: typically 2 Mbit/s or 5 Mbit/s; up to 8 Mbit/s spec.
- Payload: 0, 1, 2, 3, 4, 5, 6, 7, 8, 12, 16, 20, 24, 32, 48, 64 bytes (DLC encoding).
- Used by Bosch MG1CS / MD1CS family ECUs from ~2018.
- Read/flash a CAN-FD ECU requires a CAN-FD-capable interface (J2534 PassThru NG, KESS3, AutoTuner Master).
CAN-FD service IDs / frame structure
| ID / Code | Name | Purpose |
|---|---|---|
DLC 0-8 | Classical-CAN | 0-8 byte payload |
DLC 9-15 | CAN-FD extended | 12, 16, 20, 24, 32, 48, 64 byte payload |
BRS | Bit Rate Switch | Switch to faster data-phase |
ESI | Error State Indicator | Active vs passive error state |