A controller area network (CAN) controller unit has a message assembly buffer receiving a serial bitstream, a buffer memory coupled in parallel with said message assembly buffer, a CAN control unit coupled with the message assembly and the buffer memory, and at least one control register. The at least one control register can be programmed to cause the CAN control unit to store a message received in the message assembly register in at least a first and second mode, wherein in the first mode, control information and data payload of the received CAN message are stored in the buffer memory and in the second mode only the data payload of the CAN message is stored in the buffer memory.