| 摘要 |
PURPOSE:To obtain a digital accumulator which is used most suitably with a large frequency of accumulations by means of a simple circuit, by replacing an accumulator for carry signals with a counter which works for each generation of a 1-bit carry signal. CONSTITUTION:Input data DI 1-DI 3 are supplied to a digital adder/subtractor ALU 1 via a latch 7 and added to the preceding results of accumulation D0 0-D0 3. In this case, the carry signals C4 of the ALU 1 are counted by an up-down counter UDC 13. Here the input data is equal to a positive number and increases in the positive direction as long as the minimum bit MSB is equal to '0'. This shows the generation of a carry. While the input data is equal to a negative number and increases in the negative direction as long as the MSB is equal to '1'. Then, no carry is generated thus it is possible to discriminate the presence or absence of a carry by the signal EN obtained by obtaining the exclusive OR between the signal C4 of the ALU and the code MSB of the input data. The signal C4 and the output of a gate 11 are impressed to UDCs 12 and 13 in the form of the control signal U/D and the signal EN. Thus the desired operation is possible. |
