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Carry Lookahead Homework

Carry Lookahead Homework. You are required to calculate the performance of a 16-bit Carry lookahead adder similar to the one discussed in class. The design has 2 options assuming ripple carry is used inside each 4-bit cell Carry lookahead is used inside each 4-bit cell

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Carry Lookahead Homework

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  1. Carry Lookahead Homework • You are required to calculate the performance of a 16-bit Carry lookahead adder similar to the one discussed in class. The design has 2 options • assuming ripple carry is used inside each 4-bit cell • Carry lookahead is used inside each 4-bit cell • Both cases use carry lookahead at predicting 4-bit boundary carries [c4, c8, c12] • Draw a table showing the delay of each adder bit i.e. Sum0 - Sum 15; for each case

  2. 8-bit carry lookahead adder (4-bit block is also CLA) S0 a0 b0 3 S1 a1 b1 2nd level carry lookahead 3 S2 a2 b2 3 G0 P0 S3 a3 b3 6 4 units of delay c4= G0 + c0 P0 5 S4 a4 b4 c5= g4 + c4.p4 Delays 1 4 1 6 S5 a5 b5 6 S6 a6 b6 6 S7 G1 P1 a7 b7

  3. a0 b0 a4 b4 Result0 Result4 a1 b1 Result1 Result5 a2 b2 Result6 Result2 2nd level carry lookahead a3 b3 Result3 Result7 c4 a5 b5 a6 b6 a7 b7 8-bit CLA – uses ripple carry inside 4-bit block 0 2 2 3 4 5 6 7 4 5 6 7 8 9 10 11

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