The disclosure provides a microcontroller which has an internal timing device for generating an internal clock signal, at least one terminal contact for receiving an external clock signal, a clock changing device and a timer module, which is electrically conductively connected to the at least one terminal contact and to the internal timing device and, after the microcontroller has been switched on, is set up to determine a frequency of the external clock signal by means of the clock signal, and to determine at least one parameter by means of which the clock changing device can be set up to change the external clock signal into a useful clock signal with a predefined frequency.