Fault tolerant memory system utilizing memory arrays with hard error detection

Abstract

A fault tolerant memory system and method of operation thereof. The fault tolerant memory system includes a number of memory arrays including at least one spare memory array, wherein each of the memory arrays has an internal error detection circuit. In an advantageous embodiment, the internal error detection circuit includes an inverter, a register coupled to the inverter and a comparator for comparing the contents of the inverter and register. The comparator will generate an error signal to indicate a failed memory array in response to the contents of the inverter and register not being equal. The fault tolerant memory system also includes data correction logic that corrects data stored in a failed memory array and, in an advantageous embodiment, restores “corrupted” data in a failed array by reading the content of a row of cells in the failed memory array and generating a first complement of the content. Next, the first complement is written back to the row of cells, following which, the first complement is again read from the failed memory array and a second complement of the first complement is generated to restore the corrupted data to its original “uncorrupted” form. The fault tolerant memory system further includes a replacement circuit for replacing the failed memory array with a spare array.