| 摘要 |
PURPOSE:To clear display data in an optional area of a display screen at a high speed just with designation of a word line, by providing a mask means to the data line and supplying a prescribed write signal to a data line indicated by the mask means in a substantial read mode. CONSTITUTION:A dynamic RAM writes initial value data designated by an initial value register CDR to plural memory cells whose masks are not indicated by a clear mask shift register SRC among those (n) pieces of memory cells connected to the intersecting points between a selected word line and the complementary data lines at one side of (n) pairs. Then the RAM clears partially the memory cells connected to the word lines for each line, i.e., each word line. The memory cells can be cleared for each line by designating the lines by the external address signal and also continuously by a built-in refresh counter. In other words, said clearing action is carried out together with a selecting action of a row system in a substantial read mode.
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