Serial access memory

Details Serial access memory Serial access memory

1993-10-26

2001-10-30

Nguyen, Chanh (Department: 2675)

Computer graphics processing and selective visual display system

Plural physical display element control system

Display elements arranged in matrix

C345S566000

Reexamination Certificate

active

06310596

ABSTRACT:

REFERENCE TO RELATED APPLICATIONS
This application claims the light of priority under 35 U.S.C.119, of Japanese Patent Application Ser. No. 04-287529, filled on Oct. 26, 1992.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor memory, and particularly to a serial access memory that can be used in image processing and operated at a high speed.
2. Description of the Related Art
A serial access memory has been widely used for image processing in personal computers, word processors and the like. The serial access memory employed in image processing needs a high image-drawing speed. To meet such a demand, a device is normally used wherein a serial access memory is electrically connected to a general-purpose dynamic random access memory (hereinafter called a “DRAM”). This type of device writes data into the DRAM and thereafter reads data corresponding to a desired row, one row at a time. Then, the read data are transferred to the serial access memory, from which the data are serially read.
This type of serial access memory has been disclosed in Japanese Patent Application Laid-Open Publication Nos. 2-105388 (Laid-Open Date: Apr. 17, 1990) and 3-76091 (Laid-Open Date: Apr. 2, 1991).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a serial access memory which can be operated at a high speed.
It is another object of the present invention to provide a serial access memory which is capable of easily producing memory maps in memory cells and makes it unnecessary to provide externally-mounted elements such as a multiplexer, etc., and particularly to provide a serial access memory applicable to a Super Twisted Nematic (STN) type liquid crystal display (LCD) which is employed in office automation (OA) devices such as a laptop personal computer, a word processor, etc.
In order to achieve the above objects, the present invention provides a serial access memory comprising first and second memory cell arrays, which memory is provided with a control circuit for controlling the Most Significant Bit (MSB) of an addess supplied to each of the first and second memory cell arrays. That is, a MSB control circuit is provided which is capable of making the MSB of each address appear invalid when data is transferred from each memory cell array. Owing to the provision of the MSB control circuit, the operations of circuits in the first memory cell array become identical to those of circuits in the second memory cell array.
Further, when the serial access memory of the present invention is applied to the STN type LCD, a display device can be achieved which is capable of easily producing memory maps in memory cells and making it unnecessary to provide externally-mounted elements such as a multiplexer, etc.


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