SNIP_CLASSIC_CAN_SECTION_7_13_CAN_FD_Support

7.13 CAN FD Support For performance reasons some CAN controllers allow to use a Flexible Data-Rate feature called CAN FD (see ”CAN with Flexible Data-Rate” specification). Indicated during the arbitration phase it is possible to switch to a higher baud rate during payload and CRC. This second baud rate has to be configured by extending CanControllerBaudrateConfig with CanControllerFdBaudrateConfig. If a baud rate is active which has a CAN FD configuration (see CanControllerFdBaudrateConfig 10.2.5) the CAN FD feature is enabled for this controller. The specified second baud rate is needed to support reception of CAN FD frames with bit rate switch (BRS). Whether the second baudrate is used for transmission or not depends on configuration parameter CanControllerTxBitRateSwitch (see CanControllerFdBaudrateConfig 10.2.5). However, there may be cases where conventional CAN 2.0 messages need to be transmitted in networks supporting CAN-FD messages for example to facilitate CAN selective wakeup. In these cases it is necessary to support transmitting interleaved conventional CAN messages with CAN-FD messages. This can be achieved on frame level by using the two most significant bits of the CanId (see Can_IdType8.2.3, [SWS_Can_00416]) passed during Can_Write to indicate which kind of frame shall be used. CAN FD also supports an extended payload which allows the transmission of up to 64 bytes. This feature also depends on the CAN FD configuration (see CanControllerFdBaudrateConfig 10.2.5). Therefore, if the CAN Controller is in CAN FD mode (valid CanControllerFdBaudrateConfig) and the CAN FD flag is set in CanId passed to Can_ Write(), CanDrv supports the transmission of PDUs with a length up to 64 bytes. If there is a request to transmit a CAN FD frame and the CAN Controller is not in CAN FD mode (no CanControllerFdBaudrateConfig) the frame is sent as conventional CAN frame as long as the PDU length <= 8 bytes.