Weighted random pattern testing apparatus and method

A method for production testing of complex integrated circuit devices and producing data for diagnosing faults in those devices failing the production test, comprising the steps of;

• (a) applying a repetitive succession of structured input stimuli to the device under test,
• (b) processing the output responses of the device under test to the succession of input responses to produce a signature which is a predetermined function of the said output responses,
• (c) comparing the thus-derived signature with a signature for a known good device,
• (d) repeating the test procedure and input stimuli to produce a detailed data base on a device whose test signature fails to compare with the good signature, by
• (1) partitioning the prior test procedure into small segments of the prior test procedure,
• (2) deriving for each such segment a signature manifestive of the test results of each such segment,
• (3) comparing the thus-derived segment signature with a segment signature for a known good device,
• (4) repeating the segment test procedure for any test segment whose segment signature fails to compare with the known good segment signature, and
• (5) recording each individual set of individual input stimuli and each of the respective resultant output responses thereto to produce a detailed data base for subsequent diagnosis of the failure made of the device wherein each of the segments comprises only a fraction of the initial test procedure.