US 5,687,351 AGranted

Dual port video memory using partial column lines

AssigneeKabushiki Kaisha Toshiba

InventorHaruki Toda

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Abstract

A dual port video memory having both a random access memory and a serial access memory is provided. Memory cell column lines are provided in a memory cell array for constructing the random access memory. Each of the memory cell column lines is divided into a plurality of partial column lines. Data is sensed in each of the partial column lines in correspondence to the row selected during random access. A serial register of serial access memory is provided on each side of two adjacent memory cell column lines. These registers are connected to the two adjacent memory cell column lines via gate elements for data transfer of the random access memory and the serial access memory. By selectively controlling the gate elements, it is possible to use the four-divided partial column lines as transfer paths when deactivated, thus reducing the power consumption and improving the integration rate of the video memory. Further, the video memory is capable of providing to various transfer modes.

Claims7

Dependent claims

A video memory comprising:

a random access memory (RAM) portion having a memory cell array having a plurality of memory cells arranged in row and column directions into a matrix form, said random access memory cell array having a plurality of word lines and a plurality of column lines, each of said column lines including a pair of lines;
serial access memory (SAM) portions each composed of a pair of registers, said pair of registers including a first register and a second register, said first register being arranged on one end of two adjacent column lines and said second register being arranged on another end of said two adjacent column lines;
and
data transfer control means, arranged between said first register and each of said two adjacent column lines and between said second register and each of said two adjacent column lines, for controlling data transfer of said random access memory and said serial access memory,
wherein each of said column lines is divided into a plurality of partial column lines so that data of selected memory cells is sensed on the partial column lines in correspondence to the row selected during random access.

2 more elements

Dependencies are inferred from the claim text.