Kabushiki Kaisha Toshiba

Hitoshi Kondo

Tetsuya Yamamoto

Yukihiro Saeki

Hiroyuki Suwabe

Aiki Kojima

Hidehito Usui

Masaji Gotou

An EPROM integrated circuit includes a plurality of banks. When a data write operation is to be performed for this EEPROM integrated circuit, a bank which is used once is not used again, but the operation is constantly performed for new banks. In order to select a bank, a write number storage area is provided in the EPROM integrated circuit, and the contents of the write number storage area are updated by a write number updating circuit each time the write operation is performed for a new bank.

Nonvolatile semiconductor memory system

A programmable semiconductor memory system employs an EPROM. The system holds the start and end addresses of each write operation to completely use a data storage region of the EPROM with no redundancy and with no limitation on the quantity of data to be written if the quantity is within the capacity of the EPROM.

Semiconductor memory system

An oscillator circuit incorporated in a semiconductor integrated circuit and comprising an oscillation input terminal, an oscillator output terminal, an inverting logic circuit, and a transmission gate. The terminals and are connected to an external oscillator. The inverting logic circuit comprises an N-type MOS transistor and a P-type MOS transistor. The input and output terminals of the logic circuit are connected to the oscilllation input and output terminals, respectively. The transmission gate comprises an N-type MOS transistor and a P-type MOS transistor. Either MOS transistors has a source electrode and a drain electrode, one of which is connected to said oscillation input terminal, and the other of which is said oscillation output terminal. The gate-insulating film at least one of said MOS transistors incorporatedin the transmission gate is thicker than those of other MOS transistors formed on the semiconductor substrate.

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Yokohama, Japan

Hitoshi Kondo