Patent ID: 6993672

Claim:
A digital system that performs a specified basic function by operating a plurality of mutually interdependent flip-flops to perform digital processing according to one or more clock signals, comprising: a plurality of delay elements which are inserted respectively in a plurality of clock circuits that supply said clock signals in said digital system and each of which is composed of a circuit element that changes a delay time according to a value indicated by a control signal, and a plurality of holding circuits that hold a plurality of control signals to be given to said plurality of delay elements, wherein; said plurality of control signals having values that are changed by an external device, by (i) inputting a test signal to said digital system and observing a resultant output of the digital system and a resulting operational environment of the digital system, (ii) evaluating a fitness of the digital system from the observed output and operational environment of the digital system, and (iii) using a probabilistic search technique based on said evaluated fitness of the digital system, so that said basic function of the digital system satisfies a predetermined specification.