Program check for a non-volatile memory

摘要

A non-volatile memory has memory cells which are programmable to a programmed state from an unprogrammed state. Programming changes the conductivity of the memory cell which is being programmed. The particular state of a selected memory cell is determined by comparing the conductivity of the selected memory cell to that of a normal reference. In order to assure that a memory cell has been programmed to a conductivity which is sufficient for reliable detection, a substitute reference with a different conductivity is used immediately after programming. If the selected cell is detected as being programmed when compared to the substitute reference, the selected cell is then determined to have been sufficiently programmed for reliable detection using the normal reference.