Hitachi, Ltd.

Hitachi Vlsi Engineering Corp.

Renesas Electronics Corporation

Kazuto Izawa

Tadashi Muto

Kazuyoshi Shoji

Yasurou Kubota

Kunihiro Katayama

Koichi Seki

Yoshiaki Kamigaki

Motoki Kanamori

Atsushi Shikata

Takaaki Hagiwara

Masato Matsumoto

Shun-ichi Saeki

Shin-ichi Minami

Yuko Nabetani

Shinji Nabetani, Deceased

A controllerof a memory card is a provided with a command decoding circuitfor decoding commands issued by a host HT, a command enable registerin which the validity or invalidity of the received command, and a command detection signal generating circuitfor detecting a valid command on the basis of the result of decoding by the command decoding circuitand a value set by the command enable register. If the command enable registerreceives a validly set command, the command detection signal generating circuitwill supply a detection signal to a control unitto execute processing prescribed for each command. the command enable registerreceives an invalidly set command, no detection signal will be supplied, and the command will be ignored.

Memory card and data rewriting method

In a nonvolatile semiconductor memory device, a high voltage is selectively exerted between a word line to which the control gates of nonvolatile semiconductor memory elements are coupled and a source line to which the sources of the nonvolatile semiconductor memory elements are coupled, whereby charges stored in the floating gates are extracted through the source line. In addition, the nonvolatile semiconductor memory elements to be erased are provided with a source potential having ramp-rate characteristics such that the sources are gradually raised from a low voltage to the high voltage. Thus, the erasure of a predetermined part of the memory array of the memory device becomes possible in accordance with the division of the source lines or that of the word lines, and an excessive intense electric field can be prevented from acting between the floating gates and the sources because a ramp rate is used for the erasing high voltage.

Nonvolatile semiconductor memory device with selective tow erasure

A time circuit is provided for a nonvolatile memory device which can electrically be written into. When the write operation on a particular memory cell lasting a relatively long period of time is specified from an external device, the memory device stops the write operation on that memory cell, irrespective of the external write operaiton specification, when the time set on the timer circuit has elapsed. The nonvolatile memory device has memory cells, each consisting of a single transistor. The erase operation on the memory cells is controlled according to a current flowing through these memory cells.

Nonvolatile semiconductor memory device

Growing community of inventors

Musashino, Japan

Kazuto Izawa