Electronic adder/subtractor in BCD 8421 code with decimal display

摘要

This parallel adder/subtractor has only one dual tetrad adder/subtractor per decade. This simplification is achieved by the fact that in each decade, a storage flip flop (6) is arranged which, when H potential is present at the output (y) is activated on the right when the line (c) has H potential for a short time. The output of this storage flip flop thus continuously has a H potential as a result of which the number 6 (LHHL) is also added in the second half of this selection according to Figure 8 if this adder/subtracter is set to addition and adding takes place and the output (y) had H potential in the relevant decade. During subtraction, this parallel adder/subtracter according to Figure 8 is also switched through as a result of which the number 6 (LHHL) is also subsequently subtracted in the decades which had H potential at their output (y). <IMAGE>