| 摘要 |
The tetrad adder/subtracter according to the inventive subject matter consists of a dual tetrad adder/subtracter (main circuit 17), which can be switched over from addition to subtraction, and a correction circuit 18 for subtracting the number 6 (LHHL) and the additional circuit 5 which has the effect that in the case of addition H potential is applied to the correction circuit 18 only if the carry output y has L potential and in the case of subtraction H potential is applied to the correction circuit 18 only if the carry output y has H potential. In the case of addition, one of the two summands must be input in BCD 6 code. In the case of subtraction, both the minuend and the subtrahend are input only in BCD 0 code. Consequently, in the case of addition the number 6 (LHHL) is subtracted from the result number of the main circuit 17 when the carry output y has L potential. Consequently, in the case of subtraction the number 6 (LHHL) is subtracted from the result number of the main circuit 17 when the carry output y has H potential. As a result, the result number is present in BCD 0 code in both cases of addition and in both cases of subtraction. <IMAGE>
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