FDCAN implementation improvements over BxCAN
The below table helps users to simplify the CAN 2.0 protocol upgrade to the CAN-FD protocol in STM32 devices. This table also specifies the improvements on the FDCAN.
The FDCAN offers many advantages over the traditional BxCAN (basic extended CAN), including faster data rates and the extension of the number of data bytes that decreases the frame overhead. The bus load can be also reduced. There is an increase on the number of messages in transmission and reception that requires an improvement of the RAM memory.
| Features | Supported by BxCAN | Supported by FDCAN | |
|---|---|---|---|
| Compatibility | Compatibility with BxCAN | Yes | Yes |
| Compatibility with CAN-FD | No | No | |
| Remote frame | No | Supported to become compatible with BxCAN | |
| Frame | Arbitration bitrate /data rate (in Mbit/s) | Up to 1 (only bitrate per frame) | Up to 1 /Up to 8 |
| Data length per frame (in bytes) | 0 to 8 | 0 to 64 | |
| RAM | RAM | 512 bytes | 10 Kbytes |
| Accessible RAM | No | Yes | |
| Transmission | Dedicated Tx buffer/Tx queue/Tx FIFO | No/Yes/Yes Maximum three elements can be used as queue or FIFO. | Yes/Yes/Yes Maximum 32 elements: user chooses the transmit mechanism. |
| Transmit pause | No | Yes | |
| Reception | Dedicated Rx buffer/Rx FIFO | No/2 Up to three elements in each Rx FIFO Up to six elements maximum | 64/2 Up to 64 elements in each Rx FIFO Up to 192 elements maximum |
| Overwrite mode option | Overwrite the last element received in FIFO | Overwrite the oldest element in FIFO | |
| Improvements acceptance filters | Classical CAL (Can 2.0) acceptance filters | Some features are added as:
| |
| Other | Restricted test mode | No | Yes |
| Transceiver delay compensation | No | Yes | |
| Clock calibration unit | No | Yes | |
BxCAN developers can easily migrate to FDCAN given its BxCAN compatibility and as the FDCAN can be implemented without imposing a revision of the entire system design. The FDCAN contains all BxCAN features in an improved matter and meets the requirements for the new applications.