Panasonic Corporation

Matsushita Electric Industrial Co., Ltd.

Matsushita Electronics Corporation

Hiroaki Okuyama

Yoshinobu Yamagami

Satoshi Ishikura

Marefusa Kurumada

Toshio Terano

Hidenari Kanehara

A semiconductor memory device comprises a plurality of memory cells each including a holding circuit for holding memory data, and a read-only output circuit for outputting a signal corresponding to the data held by the holding circuit. The read-only output circuit has a read drive transistor controlled in accordance with a signal held by the holding circuit. A gate length of the read drive transistor is longer than a gate length of a transistor included in the holding circuit. Alternatively, the read-only output circuit has a read access transistor controlled in accordance with a read word select signal, and a gate length of the read access transistor is longer than a gate length of a transistor included in the holding circuit.

Semiconductor memory device

The respective sources of drive transistors included in memory cells that are located in each of multiple columns and connected to a corresponding one of bit line pairs are connected commonly to a low voltage power supply VSS via an assertion transistor. When data is written, the assertion transistor for the memory cells connected to a selected one of the bit line pairs and located in the identical column is negated, so that the sources of the drive transistors in the memory cells in that column are allowed to float. Consequently, even with a low power supply voltage, it is possible to write the data into a single selected memory cell, while data in the unselected memory cells can be retained favorably.

Low-operating voltage and low power consumption semiconductor memory device

In a system using a microprocessor including a cache memory, a specific memory cell row including at least one row of memory cells is provided to a cache memory cell array of the cache memory so as to be used as a write back buffer. When data is to be saved in the specific memory cell row (write back buffer), the memory cells aligned in one row in the cache memory cell array are selected by an arbitrary word line, and all the data to be saved are simultaneously written in the specific memory cell row (write back buffer) through bit line pairs in a batch. Therefore, since the data to be saved can be written in the specific memory cell row (write back buffer) without using a data bus, the number of accesses to be made to the cache memory can be decreased. As a result, the throughput can be improved and the power consumption of the microprocessor can be decreased. In addition, since the write back buffer is constituted by the specific memory cell row, the chip area can be decreased.

Semiconductor storage device with block writing function and reduce power consumption thereof

A static random access memory (RAM) circuit arranged such that the data stored in a memory cell is readout by detecting a transition address signal level. That is, an address transition pulse is generated by detecting an address signal transition, and first and second pulses are generated by detecting a starting edge and a trailing edge of the address transition pulse respectively. The first pulse enables a selected word line for reading out the data stored in selected memory cells. The second pulse enables an data output circuit coupled to the bit lines for transferring the readout data to an output terminal. Under such an arrangement, memory access operation becomes faster, and even if 'skew' phenomenon is caused, the transient data readout from the memory cells instantaneously is prevented from being transferred to the output terminal.

High speed static random access memory circuit

An output circuit of a static random access memory is designed to set the output voltage of the data output circuit to an intermediate voltage by detecting the transition of the address signal before the data in a memory cell is read out from the memory cell, and then, the output voltage of the data output circuit is changed from the intermediate voltage to an H level or from the intermediate voltage to an L level. In this way, since the output voltage changes from the intermediate voltage to an H level or an L level, the transition time of the output voltage is shortened, and therefore the speed of a data reading operation may be increased. At the same time, the momentary current through the data output circuit may be decreased.

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Kyoto, Japan

Hiroaki Okuyama