Detection of pattern-sensitive faults in RAM by use of M-sequencers

Claim 1

A detection method for pattern sensitive faults by use of maximum length sequences comprising the steps of: clearing a memory array; reading the memory array; checking if all memory cells of the memory array are cleared; filling a first row of the memory array with M o (=a o , a 1 , . . . ) of a fifth order maximum length sequence, a second array row with a maximum length sequence M L (=a L ,a L+1 , . . . ), a third array row with maximum length sequence (=a 2L ,a 2L+1 , . . . ), all remaining array rows n with maximum length sequences M nL (=a nL , a nL+1 , . . . ), where L and n are integers, determining a theoretical delay L between the rows in order for all patterns from 0000 to 1111 to appear in neighboring cells, the neighboring cells being defined as four neighboring cells around a base cell; reading and checking the content of each cell for the correct content such that the above steps constitute one phase; shifting the input sequences M o , M L , M 2L , . . . M nL one bit to the left in the memory array and repeating the above steps until all phase steps are completed.