JPS5475937A - Semiconductor memory - Google Patents

Abstract

PURPOSE: To enable to make a semiconductor memory good one practically even if bad memory cells such as 1 bad bit and 1 bad line exist in a memory array by adding plural preparatory memory cells to the memory array.

CONSTITUTION: The semiconductor memroy is constituted by the memory array which consists of 4096 words × 1 bit RAM and equips memory cells 4a consisting of 4096 pieces and preparatory memory cells 4b consisting of α pieces, line and column decoder circuits 5 and 6, and control circuit 7. At frist, circuits 5 and 6 are driven to investigate which line and column incoude a bad bit cell. For exmaple, when the memory cell selected by (30) of circuit 5 and (35) bad one, the decoder c ircuit which is to select (35) of circuit 6 is of circuit 6 is bad one, the decoder circuit which is to select (35) of circuit 6 is avoided to use and (35') of circuit 6 is selected by applying the same decoder as the decoder circuit to a decoder circuit for preparatory memory cell 4b. Thus, the semiconductor memory can be used as a good one practically.

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