Need help with parts a and b A carry look ahead adder computes carries separate

Question

Need help with parts a and b

A carry look ahead adder computes carries separate from sums. Say that we are adding the following 4 bit numbers:

A3A2A1A0
+B3B2B1B0
--------
The Boolean expression that defines the first carry is:

C1 = A0B0

An example of an addition for which this gives the value 1 for this carry is:

0101
+1101
-----
Since A0 = 1 and B0 = 1, thus A0B0 is equal to 1.

The Boolean expression that defines the third carry is:

C3 = A2B2 + (A2 B2)A1B1 +(A2 B2)(A1 B1)A0B0

a. Show an example addition, like the bolded addition shown above, that gives the value 1 for this third carry satisfying the third term in the expression: (A2 B2)(A1 B1)A0B0
Remember that is the operator for Exclusive OR.

b. Plug in your values in your answer to a. for A0, A1, A2, B0, B1, and B2 in the C3 formula shown above. Evaluate the operators in the following order showing the resultant expression after each step:

•   the exclusive or operators
•   the and operators
•   the final or operators

Explanation / Answer

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