Method and apparatus for locally deriving test signals from previous response signals

Abstract

An IC has local test circuitry including a test point array, instruction register, data register, probe line drivers and control/sense line drivers/receivers. To test the IC, the instruction register is loaded initiating the test circuitry to address select test points to receive control signals and to address other select test points at which response signals are to be sensed. Control signals are produced from the data register contents. The data register contents are derived as a function of the prior contents of the data register and a bit pattern formed from response signals of select test points. According to one embodiment, the prior contents are exclusively or'ed with the bit pattern of response signals to derive the new data register contents. A continuous test is performed by using prior response signals exclusively OR'ed to data register contents so as to generate subsequent control signals. Predesigned test sequences enable fast continuous testing of the IC.

Dependencies are inferred from the claim text.