Question

Given: A 4-bit adder is implemented in a carry ripple style as shown in the figure below. B3 A3 B2 A2 B1 A1 во АО FA c1 FA FA FA CO='1' SO Sought: Please calculate the output carries for each full adder (FA) using A= 0x04and B=0x04. It is required to show ALL incremental steps of the solution, then record each the final results in the table below. C4 C3 C2 ci

Answer 1

Full Adder Output two Things

1 Sum

2 Carry

Formula for Sum = A XOR B XOR Cin

Cout=  A . B + Cin ( A+B )

Now Lets Calculate for each Full Adder

We have data as A3 A2 A1 A0 = 0100 and B3 B2 B1 B0 = 0100

For FA 1

Inputs A0 = 0 B0=0 C0=1

S0 = 0 Xor 0 Xor 1 = 1

C1 = 0 + 1 ( 0+0 ) = 0

Now FA 2

Inputs A1 = 0 B1=0 C1=0

S1 = 0 Xor 0 Xor 0 = 0

C2 = 0 + 0 ( 0+0 ) = 0

Now FA 3

Inputs A2 = 1 B2=1 C2=0

S2 = 1 Xor 1 Xor 0 = 0

C3 = 1 + 0 ( 1+1) = 1

Now FA 4

Inputs A3 = 0 B3= 0 C3=1

S3 = 0 Xor 0 Xor 1 = 1

C4 = 0 + 1 ( 0+0 ) = 0

Hence we Get

S3 S2 S1 S0 = 1001

And

C4	C3	C2	C1
0	1	0	0

So We get A+ B+ C0 = 1001 = 9

This is how we can add 4 bit using Full Adder Series Circuit

Thank You

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