The main difference between CAN bus and CAN FD (Flexible Data-rate) lies in data transmission rate and payload size, but there are several specific enhancements in CAN FD over classic CAN. Here's a clear breakdown:
Classic CAN (Controller Area Network)
- Standardized as: ISO 11898-1 (original version)
- Max data rate: 1 Mbps (limited by network length)
- Payload size: 8 bytes maximum per frame
- Fixed bit rate: Same speed for arbitration and data phases
- Widespread use: Automotive, industrial automation, etc.
CAN FD (Flexible Data-rate)
- Standardized as: ISO 11898-1:2015 (updated version)
- Max data rate: Up to 8 Mbps (depends on implementation)
- Payload size: Up to 64 bytes per frame
- Dual bit rate: Slow during arbitration (for compatibility), faster during data transmission
- Improved CRC: Stronger error checking for larger frames
- Backwards compatibility: CAN FD controllers can fall back to classic CAN mode
Summary of Key Differences
| Feature | Classic CAN | CAN FD |
|---|
| Max Data Rate | 1 Mbps | Up to 8 Mbps |
| Max Payload Size | 8 bytes | 64 bytes |
| Bit Rate Switching | No | Yes (dual-speed frames) |
| CRC Check | 15/17-bit | 17/21-bit |
| Backward Compatibility | N/A | Yes (with classic CAN) |
Why Use CAN FD?
- More data in fewer messages → Reduced busload
- Faster communication → Better for high-bandwidth needs (e.g., ADAS, infotainment)
- Efficient for modern ECUs → Where both speed and payload matter