Semiconductor memory device with independently controlled reading and writing time periods

Abstract

The operating speed and stability of a semiconductor memory device of the type performing reading and writing at regular intervals are improved. A read/write pulse width controller varies the pulse width of a read/write pulse width control signal in such a manner that the width during reading is shorter than that during writing. A column decoder outputs a column-select signal having a pulse width equal to that of the read/write pulse width control signal. And a column-select gate connects an associated pair of bit lines to a pair of data lines while the column-select signal is high. During reading, a sufficiently long time can be allotted for equalizing potentials on the data lines. On the other hand, during writing, plenty of time can be allowed for connecting a pair of data lines to the pair of bit line. As a result, reading and writing can be performed stably enough at a sufficiently high speed.