Invention Grant
US08015457B2 Redundancy circuit and semiconductor memory device 有权
冗余电路和半导体存储器件

Redundancy circuit and semiconductor memory device
Abstract:
Disclosed is a circuit for deciding whether or not a plural number of redundancy ROM circuits have been programmed in a preset order, with regards to addresses. In at least one of first to n-th redundancy memory circuits, an address to be substituted by a redundant address is recorded and a redundancy selection signal is output when an access address is coincident with the programmed address. It is presupposed that repair addresses are programmed from the first to the n-th redundancy ROM circuits in an ascending order with regards to address. If it is detected under this condition that a redundancy selection signal has been output from the i+1'st redundancy memory circuit while no redundancy selection signal is being output from the i-th redundancy memory circuit, an SR flip-flop is set and the sequence of the substitution decision outputs is decided to be a reversed sequence.
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