Your task in this question is to analyse the logic circuit shown in Figure 2. Th
ID: 2989564 • Letter: Y
Question
Your task in this question is to analyse the logic circuit shown in Figure 2. The inputs to the circuit are C0, A0, B0, A1, B1, A2 and B2. The outputs are S0, S1, S2 and C3. The internal structure of the logic block in the middle of Figure 2 is shown in Figure 3.
The circuit has seven inputs so while you might like to try a few different input com- binations to get a feel for the circuit, I suggest that you do not attempt to construct a full truth table. Rather, you should derive expressions for the outputs and see if you can make sense of the resulting expressions to determine what this logic circuit does.
Explanation / Answer
Ans: the equations according to the circuit diagrams
c3 = g2 + g1 p2 + g0 p1p2 + c0p0p1p2
c2 = g1 + g0 p1 + c0p0p1
c1 = g0 + c0 p0
g2 = A2B2,g1=A1B1,g0=A0B
p2 =A2 XOR B2;p1=A1 XOR B1;po=A0 XOR B0
s0=c0 xor p0;
s1=c1 xor p1;
s2=c2 xor p2;
The above logic its berfomig 3 bit addition based on carry look ahead addition, where the each stage of carry its not depends upon previous carry out like carry ripple adder, and the addition take place parrallely.
the genreal equations are
Generate signal: gi = xiyi
Propagate signal: pi = xi xor yi
Carry recurrence ci+1 = gi + cipi
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