The IC is shown in the Simplified Block Diagram. The chip can select between one of two sensors, if needed for accurate monitoring or for "V" type engines. Internal control via the SPI bus is fast enough to switch sensors between each firing cycle. A programmable bandpass filter processes the signal from either of the sensor inputs. The bandpass filter can be selected to optimize the extraction the engine knock or ping signals from the engine background noise. Further single processing is obtained by full wave rectification of the filtered signal and applying it to an integrator whose output voltage level is proportional to the knock signal amplitude. The chip is under microprocessor control via a SPI interface bus.