Q. How to input to circuit?
The input carry Cin that can be equal to 0 or 1 goes to carry input of the full adder in least significant position. Other carries are cascaded from one phase to the subsequent. Logically it is same as that of addition performed by us. We do pass carry of lower digits addition to higher digits. The output ofbinary adder is determined from the below arithmetic sum:
D = X + Y + C_{in}
OR
D = A + Y + Cin
By controlling value of Y with the two selection lines S_{1}and S_{0} and making C_{in} equal to 0 or 1 it's possible to implement eight arithmetic micro-operations listed in truth table.
Figure: Arithmetic Circuit Function Table