PURPOSE: To take an effective test of a memory chip having redundant cells, by obtaining a defective cell distribution map used effectively for the relieving of a chip which has defective cells to be relieved.
CONSTITUTION: When even an defective cell is present in each line (row or column), a fail register FREG stores 1, which is used for relieving. A fail cell counter FCCT counts and stores the number of defective cells in each line. When addresses X and Y of a defective cell are new, a fail address recorder FADCX allocates one of linear memories FBLM for defective bit writing on the X side to an address equal to the X in the memory incorporated in the recorder, thereby writing defect information in an address equal to the Y in the FBLM. A fail counter FLC counts up when addresses X and Y are both new to check on whether the counted value exceeds the number of redundant cells or not. When relieving is possible, a defective cell distribution position map is utilized for it.
TAKAHASHI MASUO
MAKI KATSUHIKO
