Serial tetrad adder/subtractor in BCD-8421 code

摘要

This tetrad adder/subtractor exhibits as the main circuit a dual tetrad subtractor 1 and exhibits as correction circuit a subtracting circuit 2 for the subtraction of the number 6 and which exhibits a nines complement circuit 8 combined with a code conversion circuit 7 because a code conversion circuit is required as additional circuit for the nines complement circuit. The code conversion circuit 7 converts BCD-8421-coded decimal numbers into decimal-1-of-10-coded decimal numbers. The nines complement circuit 8 supplies the nines complement number of the respective decimal-1-of-10-coded output number of the circuit 7, in BCD-8421 code. During the subtraction, the B inputs are the minuend inputs and the A inputs are the subtrahend inputs and the input E is at L potential and line c has H potential. During the addition (subtractive addition), input E is at H potential and line b thus has H potential. <IMAGE>