| 摘要 |
PURPOSE:To execute a read/modify/write action over consecutive two bits by adding a shift starting position control part and a shift range control part for consecutive two bits to a nibble shift register of four bits. CONSTITUTION:Based on a nibble address of lower two bits supplied to the shift starting position control part 12, one output terminal of a decoder D goes to H-level, and the output of a gate G1 goes also to H-level. This causes a selection signal Y1 from an FF11-1 to turn to H-level to read a data from a memory cell block M1. At this point of time of said reading, an L-output from the FF11-1 is sent to a gate G2 to read a from a memory cell block M2. At the ending time of this read, a selecting signal SEL goes to H-level, and a data-write to the block M2 is executed. In such a way, a signal SEL is shifted to H-level only at the ending time of a second-bit read in order to re-set on FF in the precedent stage, thus a read/modify/write action over two bits is executed.
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