Measuring a control system response time of a second clock tree is provided, comprising measuring a skew between the second clock signal and the first clock signal and storing the skew, initiating a delay change of a delay induced by the programmable delay line and starting a time measurement. At least one iteration is performed of measuring the skew between the second clock signal and the first clock signal and comparing the measured skew with the stored skew. Based on the result of the comparison, stopping after a current iteration and stopping the time measurement. A result of the time measurement is the control system response time.