ECE 645: Spring 2005

Practice Exam I

20 points total

Part I  (8 points)

  1. (1 point) Match the following 5-bit representations of -12 with the names of these representations:

    A. 11100
    B. 10100
    C. 00100
    D. 10011

    a. biased with B=24
    b. one's complement
    c. two's complement
    d. signed-magnitude


  2. (1 point) Arrange the following signals in the order they are generated within the 64-bit 3-level carry lookahead adder, starting from a signal that is generated first. Assume that the adder is built of AND, OR, and XOR gates, and that delays of all these gates are equal.

    A. c53
    B. c8
    C. g[36, 39]
    D. c48
    E. s15

  3. (1 point) Arrange the following numbers in the ascending order:

    A. (3A)16
    B. (152.26)-10
    C. (2 -2 3 -3)4
    D. (111.33)1/10
    E. (1 0 -1 1 -1)3

  4. (1 points) Arrange the following 16-bit adders in the order of increasing worst case delay. Assume that all adders are built of AND, OR, and XOR gates, and that the delays of all these gates are equal. Every adder accepts carry-in and produces carry-out.
  1. ripple-carry adder
  2. Kogge-Stone Parallel Prefix Network adder
  3. Brent-Kung Parallel Prefix Network adder
  4. 2-level carry-lookahead adder
  5. 3-level carry-select adder based on short ripple carry adders

5. (1 point) Determine all outputs of an 8-bit carry-save adder fed with the following three numbers:

0111 1101

1101 0110

0110 1110

6. (1 point) Using dot notation, show addition of eight 5-bit numbers in the Dadda's tree.

7. (2 points) Compute the product of the following two elements of the Galois Field GF(28): 'A6' and 'B8'. Assume that an irreducible polynomial P(x) is equal to P(x)=x8+x4+x3+x+1


Part II (12 points)

  1. (3 points) Design a 16-bit adder using the following components: 16-input Kogge-Stone parallel prefix network (Parhami, Fig. 6.10) built of NAND gates, supplemented with additional NAND gates. Estimate the delay and area of this adder expressed in the number of gate levels and the number of NAND gates respectively.
  2. (3 points) Determine all bits of the ANSI/IEEE standard single-precision representation of the following numbers:

    a. 250.5312510
    b. 0 infinity
    c. -1.234510 / 0
    d. -1.0110112 2-140

  3. (3 points) Design a minimum-area 10-bit counter that counts in steps of 5 starting from 0 to 1000, and then resets itself and starts counting again. Assume that you can use the following components in your design: half-adders shown in Parhami, Fig. 5.1, full-adders shown in Parhami, Fig. 5.2a, and additional NAND gates.
  4. (3 points) Using dot notation, show the addition of seven 4-bit numbers in the Dadda Carry- Save Adder tree. Draw a detailed schematic of the entire adder corresponding strictly to your dot diagram, using only full adders, half adders, and NAND gates. Estimate the delay and area of your circuit, assuming that the full adders and half adders are built of NAND gates.