Worst Case Delay for Ripple Carry Adder

Discussion in 'Homework Help' started by d3ck, Feb 6, 2014.

  1. d3ck

    Thread Starter New Member

    Jul 14, 2013
    I didn't get what my teacher said about worst case delay. The question sound like this:

    Given 4-bit RCA with different delays, find the worst case delay for the adder

    tcarry(0->1) = 400pS
    tsum(0->1) = 500pS

    tcarry(1->0) = 500pS
    tsum(1->0) = 600pS

    Since the RCA delay formula;
    tadder = (N-1)tcarry + tsum

    I assume carry will affect more to the overall delay. And my best guess is when A = 0101, B = 0101, worst delay will occurs because carry will change from 1 to 0 two times in the adding process. Am I correct?