Question

The carry propagation can be expressed as ________

(a) Cp = AB

(b) Cp = A + B

(c) All but Y0 are LOW

(d) All but Y0 are HIGH

The question was posed to me during an interview.

My doubt stems from Combinational Circuits topic in division Combinational Circuits of Digital Circuits

Answer 1

Right choice is (b) Cp = A + B

Best explanation: This happens in parallel adders (where we try to add numbers in parallel via more than one adders). A carry propagation occurs when carry from one adder needs to be forwarded to other adder and that second adder is holding the computation (addition) because carry from first adder has not come yet. So, there is a slight delay for second adder and this is known as carry propagation.