A method and apparatus for monitoring a plurality of semiconductor devices is disclosed. At least one array of 2.sup.n semiconductor circuits is provided. A clock ring oscillator provides a clock signal. The clock signal drives a frequency divider followed by an n-stage binary counter. The outputs from the counter's stages drive an n-input decoder which sequentially addresses each semiconductor circuit. An output signal from each semiconductor circuit is measured and read out over a common bus, where a distribution of the output signals is a measure of a distribution of a parameter of interest.