Kabushiki Kaisha Toshiba

Masaya Kubota

Kiyoharu Oikawa

Yasuhiro Watanabe

Kimio Maruyama

Naokazu Kuzuno

Yukihiro Nishida

Junji Morita

A memory data protection system is disclosed, which comprises a memory circuit, a protection contents indicating section which stores a security bit and a protection bit, a protection function circuit which determines permission/prohibition of reading of data from the memory circuit and permission/prohibition of writing of data to the memory circuit in accordance with the security bit and the protection bit, and a protection function locking/unlocking circuit which makes the protection function circuit in a lock state to forcibly prohibit reading of data from the memory circuit and writing of data into the memory circuit in a time period from when a power supply is turned on till when the protection function circuit completes reading of the security bit and the protection bit from the protection contents indicating section into data buses, and after lapse of the time period, the protection function locking/unlocking circuit unlocks the lock state.

Memory data protection system

A plurality of dummy cells which generate reference potential corresponding to a capacitance of a bit line each have a floating gate, control gate and first and second diffusion layers. The first and second diffusion layers of each dummy cell are commonly connected by use of a wiring.

Nonvolatile semiconductor memory device containing reference capacitor circuit

A redundancy fuse circuit including a function of replacing a defective cell in a memory cell array with a redundancy cell, comprising a fuse circuit in which an address of the defective cell or a block including the defective cell is programmed as a defective address by presence/absence of cut-off of a fuse, a data latch circuit which latches a signal supplied from a tester to program the defective address in a dummy manner, and a comparator which replaces the defective cell with the redundancy cell based on an address signal supplied from the tester and an output signal of the data latch circuit at an operation confirmation time of the redundancy fuse circuit.

Growing community of inventors

Kawasaki, Japan

Masaya Kubota