| 摘要 |
PURPOSE:To simplify the constitution without an adder by storing digital highway signals of plural periods. CONSTITUTION:When data DA is inputted to a memory write control circuit 1 from a digital highway line, it is outputted together with a memory write signal SW and a memory address MA, and stored in a memory 2. Receiving an indicating signal SD from the memory write control circuit 1, a memory read control circuit 3 reads out n-pieces of data DA of the same bit number and a bit information DB0, both of which are compared in a bit comparing circuit 4. When a change is detected, a change detecting signal SV and a new bit information DB1 having contents of the data DA are outputted, and the bit information DB1 is written in the change detection data storage block of the memory 2.
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