Communication system having: a) a CAN bus; b) at least two devices (30, 40) coupled by means of the CAN bus, wherein at least two of the devices (30, 40) coupled by means of the CAN bus have: b1) a CAN control unit that is suitable for transmitting CAN data frames via the CAN bus by means of a first physical protocol in a first transmission mode; b2) an asynchronous serial communication interface unit that is suitable for transmitting ASC data frames via the CAN bus by means of a second physical protocol in a second transmission mode, and b3) a switching means that is connected to the CAN control unit and that is connected to the asynchronous serial communication interface unit by a second line, wherein the switching means is suitable for changing over between the first transmission mode and the second transmission mode on the basis of at least one agreement valid between the respective device and at least one further device, b4) a memory device for storing a control program, wherein the agreement is at least partly configured as part of the control program, b5) a driver device that connects the switching means to an interface device, wherein the interface device is configured to couple the respective device to a further device via the CAN bus, characterized in that the agreement comprises in which predetermined time window(s) the respective switching means of a predetermined number of devices (30, 40) switches to the first transmission mode or to the second transmission mode. a) a CAN bus; b) at least two devices (30, 40) coupled by means of the CAN bus, wherein at least two of the devices (30, 40) coupled by means of the CAN bus have: b1) a CAN control unit that is suitable for transmitting CAN data frames via the CAN bus by means of a first physical protocol in a first transmission mode; b2) an asynchronous serial communication interface unit that is suitable for transmitting ASC data frames via the CAN bus by means of a second physical protocol in a second transmission mode, and b3) a switching means that is connected to the CAN control unit and that is connected to the asynchronous serial communication interface unit by a second line, wherein the switching means is suitable for changing over between the first transmission mode and the second transmission mode on the basis of at least one agreement valid between the respective device and at least one further device, b4) a memory device for storing a control program, wherein the agreement is at least partly configured as part of the control program, b5) a driver device that connects the switching means to an interface device, wherein the interface device is configured to couple the respective device to a further device via the CAN bus, characterized in that the agreement comprises in which predetermined time window(s) the respective switching means of a predetermined number of devices (30, 40) switches to the first transmission mode or to the second transmission mode. b1) a CAN control unit that is suitable for transmitting CAN data frames via the CAN bus by means of a first physical protocol in a first transmission mode; b2) an asynchronous serial communication interface unit that is suitable for transmitting ASC data frames via the CAN bus by means of a second physical protocol in a second transmission mode, and b3) a switching means that is connected to the CAN control unit and that is connected to the asynchronous serial communication interface unit by a second line, wherein the switching means is suitable for changing over between the first transmission mode and the second transmission mode on the basis of at least one agreement valid between the respective device and at least one further device, b4) a memory device for storing a control program, wherein the agreement is at least partly configured as part of the control program, b5) a driver device that connects the switching means to an interface device, wherein the interface device is configured to couple the respective device to a further device via the CAN bus,