| 摘要 |
The subtraction circuit according to the subject of the invention is not a true subtraction circuit, but a substitute subtraction circuit, which forms the subtraction result numbers additively, by adding the nine's complement number of the subtrahend to the minuend. This subtraction circuit is therefore provided with a nine's complement circuit (80). This nine's complement circuit (80) is a special nine's complement circuit, which supplies the nine's complement number in 5221 code. If a subtraction has only a circuit carry and thus no real carry, the carry output (y) has high potential. If a subtraction has no circuit carry and thus a real carry, the carry output (y) has low potential. <IMAGE>
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