Isolation/removal of faults during lbist testing

Abstract

A method of LBIST testing of an entire chip (i.e. all logic and arrays are getting system clocks) enables finding intermittent fault in an area, such as the L1 cache. Latches such as GPTR latches can be set such that the L1 cache will no longer receive system clocks during LBIST testing. Logic causing an intermittent failure will no longer receive system clocks and hence will no longer cause intermittent LBIST signatures. LBIST testing can proceed on looking for the next failure, if one existed, or proving that the remaining logic contains no faults. Generally, a chip, has a basic clock distribution and control system that the chip is divided into a number (N) of functional units with each unit receiving system clocks from its own clock control macro. Each clock control macro receives an oscillator signal and a bit from the GPTR (General Purpose Test Register). All the functional units contain latches that are connected into one scan chain.