Serial tetrad addition and subtraction device in BCD 8421 code with negating-complementing circuit

摘要

The object of the invention is a tetrad addition and subtraction device in BCD 8421 code, which has: - as the main circuit, a dual tetrad adder (1) - as the correction circuit, a subtraction circuit (2) to subtract the number 6 - a pre-adder circuit (3) to add the number 6, by which the number 6 is added to the summand at the A inputs when addition takes place - for carrying out additive subtractions, a negating-complementing circuit (4), which is a 15s-complement circuit for BCD 8421 coding. Thus, in this addition and subtraction device, additions are carried out normally, and subtractions by additive subtraction. For subtraction, the B inputs are the minuend inputs, and the A inputs are the subtrahend inputs. For addition, in circuit (4), the complement bypass is pre-triggered, and the pre-adder circuit (3) is pre-triggered. For additive subtraction, in circuit (4), the complementing is pre-triggered, and the pre-adder circuit (3) is not pre-triggered. <IMAGE>