| 摘要 |
PURPOSE:To shorten the processing time with a priority encoder by providing a mask generating part, a zero deciding part and a mask control part and applying a tree retrieving method to retrieve the highest rank valid bit of the data stored in an input register. CONSTITUTION:In an example where the input is set at '0010100', a mask control part 4 outputs the first value '4' of a tree structure in a 1st cycle. Then, the lower rank 4 bits of the input data are masked and '00010000' is supplied to a zero deciding part 3. Thus, the part 3 outputs the deciding result '0' and the part 4 receives this result '0' in a 2nd cycle to output '6' to the lower left side. The lower rank 6 bits of the input data are masked and '00000000' is inputted to the part 3 with the deciding result set at '1'. In a 3rd cycle, the output of the part 4 moves down to the right side and set at '5'. Thus the five lower rank bits of the input data are masked and '00000000' is inputted to the part 3 with the deciding result set at '1'. Thus the final result '4' of a binary tree is obtained.
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