| 摘要 |
PURPOSE:To reduce the word writing time while holding the contents of a specific bit as they are for the write data, by invalidating selectively the writing to >=1 bit in a word to be written. CONSTITUTION:The write data given from a write data bus 2 is processed by an AND circuit 7 together with a write enable signal sent from a write enable signal line 5. The signal is delivered to a write enable line 6 from the circuit 7 only when the write data and the write enable signal are set at (1) respectively, and a specific bit of a word in a storage region 1 is written. Otherwise the writing of the specific bit is invalidated, and the old data is held as it is. Therefore it is not needed to read out and store temporarily the old contents and to produce the new contents from the contents stored temporarily for writing. Thus the word writing is carried out quickly and in short time, while holding the contents of a specific bit of the write data as they are. |
