GATE 2016 CS (CS2) – Question 17
An eight-bit ripple-carry adder computes A + B for two’s-complement integers. A = 1. Find the decimal B that causes the longest sum-settling latency.
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Correct answer: -1.0 to -1.0
Explanation
Choose B=11111111. With A=00000001, the least significant position generates a carry and every remaining position propagates it through the full chain. This causes the longest settling path. The eight-bit two’s-complement value 11111111 is −1.