Embodiments of a device and method are disclosed. In an embodiment, a CAN device includes a security module connected between a CAN bus interface of a CAN transceiver and a microcontroller communications interface of the CAN transceiver and an operational mode controller connected between the security module and the CAN bus interface. The security module is configured to perform a security function on data traffic received from the CAN bus interface or from the microcontroller communications interface. The operational mode controller is configured to set an operational mode for the CAN transceiver such that a CAN Flexible Data-rate (FD) frame or a corresponding CAN frame is output from the CAN bus interface. An identifier of the CAN FD frame is the same as an identifier of the corresponding CAN frame.