| 摘要 |
PURPOSE:To realize a redundancy circuit which is very simple in circuit configuration and small in occupying area, by automatically forming a signal which designates a preliminary memory group from a signal change-over circuit, and outputting the signal to a preliminary decoder. CONSTITUTION:An address signal, by which a preliminary memory column 3s is selected against a preliminary Y-decoder 6 when a prescribed address signal is inputted. The preliminary Y-decoder 6, for example, is set to a condition where its output attains a high level (selecting level) when the signal supplied from the signal change-over circuit 5 attains low level. By the output of the selecting level of the preliminary decoder 6, all the outputs of a normal Y-decoder 2 are inhibited and a column switch which selects a preliminary column 3s is turned on. That is to say, when the output of the preliminary Y-decoder attains a high level, any memory columns containing defective bits in a normal memory array 3 are not selected and the preliminary column 3s is selected instead of the former. |
