Fujitsu Corporation

Haruo Shoji

Tetsuji Takeguchi

Junya Kawamata

Hideyuki Furukawa

Takaaki Ichikawa

Tomomi Furudate

Masato Kitamura

Yuzuru Matsuno

Tatsuya Yoshimoto

The present invention aims at providing a semiconductor memory device that can be operational in a desired boot block mode, regardless of the original boot block type of the device, by facilitating rewriting of the memory device. A sector address from an outside source is inputted into a sector-address conversion circuit, which converts the sector address into an internal address, and a memory cell array is accessed through an address decoder circuit. Suppose that each of banks of the memory device is configured as a bottom boot type. By converting the sector address by the sector-address conversion circuit such that the sector-address now appears to the outside in the reverse order, each of the banks now functions as a top boot type.

Semiconductor memory device, a sector-address conversion circuit, an address-conversion method, and operation method of the semiconductor memory device

A plurality of memory cells corresponding to an address space larger than 2and smaller than 2, an invalid address detecting circuit, and an invalid signal outputting circuit are comprised. Upon command input, the invalid address detecting circuit invalidates a command in the case where the invalid address detecting circuit detects a fact that an address signal supplied from exterior indicates an invalid address space. Therefore, at the time of invalid address supply, internal circuits are not activated and an erroneous write or erase operation can be prevented. Since the internal circuits do not operate, power consumption can be reduced substantially. The invalid signal outputting circuit outputs an invalid signal by receiving the fact of invalid address signal detection by the invalid address detecting circuit. Therefore, a system unit mounting the semiconductor memory device can easily recognize that the invalid address signal has been supplied to the semiconductor memory device. As a result, a malfunctioning can be prevented and reliability of the system unit improves.

Semiconductor memory device and method of controlling same

A semiconductor memory device which can reduce a time required for a write-protection setting operation when a plurality of blocks are to be write-protected. A write area of the semiconductor memory device is divided into a predetermined number of blocks each of which is rewritable on an individual block basis. Write-protection information is simultaneously provided to a plurality of blocks that are arbitrarily designated from among the predetermined number of blocks so that the plurality of blocks are simultaneously subjected to the write-protection setting operation.

Semiconductor memory device for reducing a time needed for performing a protecting operation

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Kawasaki, Japan

Haruo Shoji