| 摘要 |
PURPOSE:To improve the yield of a memory device by providing externally a spare memory, writing a defective bit address into an associative memory to access newly the spare memory thereby increasing remarkably the number of relieved defective bits. CONSTITUTION:The associative memory 4 is used to relieve a memory having defective cells by means of software redundancy technology, the defective cell address is stored in an associative decode section, the same address 13 as the external address is outputted selectively by a selector circuit at the access of the external address 22 and when it is retrieved and coincident, a new address (outputted to an internal address bus 14) of the spare memory located at the data part of the associative memory is selected and the result is fed to an internal address bus 15 by using a coincidence detection signal 21. On the other hand, when dissident, the external address 22 is fed to the bus 15. The information of the associative memory is kept permanent by a battery 11 and a backup circuit 10 in constituting the memory of a static memory.
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