Mixed signal integrated circuit

This invention relates to mixed signal integrated circuits, that is, integrated circuits comprising both analog and digital circuitry. More particularly, it concerns reduction of noise in such a device. When a digital circuit is included in the same integrated circuit device as an analog circuit, the digital circuit may be an additional source of a considerable amount of noise. This results in cross-talk, electrical interference and signal distortion imposed on the analog signals. The invention provides an integrated circuit comprising analog circuitry and digital circuitry wherein the digital circuitry includes an ASM. An ASM does not require a clock signal. Its operation is triggered by appropriate input conditions, but in contrast to an SSM it is idle when there in no change in its inputs, lowering the level of noise generated by the digital circuitry.