REDUNDANCY SCHEME FOR AN MOS MEMORY

摘要

An MOS memory has a main array of memory cells (10, 12) and a plurality of spare memory cells (22, 24). Typically, each memory cell is tested for operability by a conventional probe test. A redundancy scheme is provided for substituting spare memory cells for memory cells found to be defective. An on-chip address controller (38-50) responds to the probe test finding a defective cell by permanently storing and rendering continuously available a fully asynchronous electrical indication of the address of the defective cell. The address controller (38-50) compares its stored data with memory cell information received during normal memory operation, and generates a control signal indicative of the receipt of an address which corresponds to a defective cell. A spare cell selector (106, 108) responds to the control signal by electrically accessing a spare memory cell and by prohibiting access of the defective memory cell.