Question 10.21: Draw and explain the block diagram of a 4 bit binary adder....
Draw and explain the block diagram of a 4 bit binary adder.
We can simplify the representation of half-adder and full-adder circuits by drawing only a box with the input and output lines, as shown in Fig. 10.11. When drawing multibit adders, a block diagram is used to represent the addition in each column.
For example, in case of a 4-bit adder, the 2^{0} column needs only a half-adder, because there will be no carry-in. Each of the more significant columns requires a full-adder as shown in Fig. 10.12.
Note that the LSB half-adder has no carry-in. The carry-out \left(C_{\text {out }}\right) of the L S B becomes the carry-in \left(C_{\text {in }}\right) to the next full-adder to its left. The carry out \left(C_{\text {out }}\right) of the M S B full-adder is actually the highest-order sum output \left(\Sigma_{4}\right).
