Abstract: A memory device, which communicates with external address and data buses, includes a circuit for mapping a redundant memory column having a redundant memory cell to an address of a defective memory column. An enable line communicates with the redundant memory column and selectively carries active and inactive signal levels for respectively enabling and disabling communication between the data bus and the redundant memory cell. An address decoder receives an address signal on the address bus and generates the active level on the enable line when the value of the address signal equals the address of the defective memory cell. A driver precharges the enable line to the inactive level while the address signal is invalid.

Abstract: An apparatus maps one of a plurality of redundant memory columns, each having a redundant memory cell, to an address of a defective memory column in a memory device that communicates with an external data bus having one or more data-bit lines and an address bus. An address decoder receives an address signal on the address bus and generates an enable signal to enable the redundant cell of the redundant column when the value of the address signal equals the address of the defective memory column. A bit-select bus has one or more bit-select lines each associated with one of the data-bit lines. Each bit-select line can carry a bit-select signal. Each of a plurality of bit-line selectors is associated with one of the redundant columns and communicates with the bit-select bus. In response to an associated enable signal, each bit-line selector can generate the bit-select signal on the bit-select line associated with a desired data-bit line.