Frequently Asked Questions

  • Yes, a node that is CAN-FD capable can communicate on classic CAN as long as the FD exclusive flags are not enabled. 

    It will not be able to use the faster data rate as the faster speed will cause error frames due to mismatched timings. 

    It will also not be able to transmit more than 8 data bytes at a time due to the reason above. 

  • No, the mismatched bit rates will cause error frames as the nodes will be trying to decode the messages using mismatched timings. 

  • Standard termination is suitable for most situations, split termination is used when communication robustness is critical. The resistors and capacitor increases the networks resistance to noise, improves signal stability and reliability. 

  • Due to how fast CAN transmits signals, the two wires act like transmission lines. When the signal reaches the end of the wire, the signal will reflect back. The termination resistors absorb that energy preventing the reflection. 

  • Due to ISO. The maximum cable lengths and resistor values are set to make it easier for use as well as ensuring reliability. The resistor values are calculated based on the impedance of the network which has a set maximum length. 

  • Bit rate = number of bits per second 

    Baud rate = number of data units(symbols) per second 

    Since a data unit in CAN is only 1 bit, there is no difference between the two rates and the term can be used interchangeably.

  • It gives users a larger selection of identifiers to use.  Gives finer control over message priority due to number of available identifiers.  

    It does come with a drawback, the data rate would be slower if the same bit rate is used because the CAN message now has more bits to transmit. 

  • No, it only confirms that the message was sent with the expected bytes. It does not confirm if the bytes that were sent had the correct data.

  • When a node is trying to set the network into a recessive state, the transceiver doesn't actually send or do anything. It sits in a passive state. 

    The only time the transceiver does something active is when it tries to set the network into a dominant state . The transceiver will actively send a voltage onto the network. 

    Due to this, a dominant state will always overwrite a recessive state.  

    All nodes will initially transmit only up to the end of the ID section of the CAN frame. The node will only transmit the rest of the frame if all of the ID is successfully transmitted.  

    Essentially the highest priority ID will bulldoze over everything else.