Importance

Loading Importance Indicators...

Abstract

To locate soft cells in a memory cell array, a known logic pattern is written in the memory array. The word lines for the array are then sequentially subjected to a nonstandard test signal such as a slowly varying voltage. Word lines are returned to VCC and the array is then interrogated to identify memory cells which have flipped logic states. These cells are identified as soft or potentially defective cells. The process can be repeated with the logically opposite logic pattern being initially stored in the array. Apparatus is provided for implementing this process on a standard RAM memory cell array. An access pad is added for receipt of an externally generated test signal. A control circuit selectively couples the test signal to the word lines for the memory array.

Loading the Abstract Image...

First Claim