Method, circuitry and device for spreading a clock signal in which the clock signal is received at an input of a variable delay line, the clock signal having been generated by a clock signal generator. In one embodiment, for each edge of the clock signal, the delay introduced by the variable delay line is set in accordance with a stored delay value. For each of a plurality of consecutive edges of the clock signal, the stored delay value is either incremented or decremented based on a randomly generated value for that edge. A spread version of the clock signal is output from the variable delay line, wherein each edge of the spread version of the clock signal is delayed by the respective delay that is set for that edge of the clock signal.