Chip protection register lock circuit in a flash memory device

摘要

A chip protection register lock circuit uses a plurality of lock bits in a lock bit register. If the register contains N bits, N/2 bits of the register are coupled to an erase circuit and the remaining N/2 bits are coupled to a programming circuit. After the chip protection register is programmed, the group of N/2 bits coupled to the erase circuit are erased and the remaining N/2 bits are programmed such that an alternating pattern of logical ones and zeros are in the lock bit register. A read and compare circuit generates a lock indication if the alternating pattern is present.