Switching Back

With more data comes a demand for a larger Cyclic Redundancy Check. Depending on the size of your data, the CRC may require anywhere from 15 to 32 bits to get the same protection of the data frame. If an error is detected in the CRC, an error frame will not be sent until after the end of frame as you cannot interrupt during push-pull mode.

To return to the normal bus speed and dominant-recessive mode, we now have a dominant to recessive edge to synchronize all receivers, then we have the DAH, data-to-arbitration bit, which will indicate to the CAN XL drivers to return to dominant recessive level at the same time returning to the original speed with a second dominant to recessive edge to ensure there will be no clock variation offset when switching.

The End of Frame (EOF) is the same across all versions of CAN as we have returned to arbitration. At the start of the EOF will be the acknowledgement bit which all senders will transmit as recessive, and all recipients will transmit as dominant. To indicate to the sender that all is okay. If something has gone wrong, the recipient will transmit this bit as recessive and after the acknowledgement delineator they will send an Error Frame. This is important as this step ensures all receivers on the bus get exactly the same information.