CSCE 488, fall 2001                                             HOMEWORK 2

Due Date: Wednesday, September 26, 2001


Purpose: This assignment will serve as a prerequisite test and, at the same time, provide practice on technical reading comprehension and bibliogrpahic searches. As with Homework 1, you are to mail your results in a single pdf file to Prof. Scott by 8:30am on the due date.

Problem 1: First read carefully the paper ``Binary decision diagrams,'' by S. B. Akers. Then consider the following netlist that describes a sequential circuit in a self-evident format.
 

# 4 inputs
# 1 outputs
# 3 D-type flipflops
# 2 inverters
# 8 gates (1 ANDs + 1 NANDs + 2 ORs + 4 NORs)

INPUT(G0)
INPUT(G1)
INPUT(G2)
INPUT(G3)

OUTPUT(G17)

G5 = DFF(G10)
G6 = DFF(G11)
G7 = DFF(G13)

G14 = NOT(G0)
G17 = NOT(G11)

G8 = AND(G14, G6)

G15 = OR(G12, G8)
G16 = OR(G3, G8)

G9 = NAND(G16, G15)

G10 = NOR(G14, G11)
G11 = NOR(G5, G9)
G12 = NOR(G1, G7)
G13 = NOR(G2, G12)

Analyze the circuit and draw a BDD for the primary output G17 and the secondary output G11. You should constrain your BDD to be an ordered BDD (OBDD) in which a fixed ordering of variables is used. That is, if there are four variables in the diagram and they are ordered as x(1), x(2), x(3), and x(4), then the following conditions must be satisfied in an OBDD:

    (1) indices of variables on any path from a root to a leaf are always encountered in strictly increasing order, and
    (2) a variable may occur at most once in any such path.

A careful choice of ordering can yield great simplification of the resulting diagram. Therefore think carefully about the ordering you choose and provide arguments in favor of its use.

Problem 2: After you finish reading the Akers paper, describe in your own words the content of the article, in abstract format and limiting yourself to ten sentences.

Problem 3. This exercise involves searches of bibliography and citation indices related to the topic of the Akers paper.

(a) Using the INSPEC database, accessible from UNL Libraries' IRIS system, search for the journal papers on binary decision diagrams published since 1975. Include your results in your pdf file.

(b) Using the  Reseach Index (Citeseer) find five recent papers (from any source: journals, conferences, or technical reports) that apply BDDs to logic synthesis. Find five recent papers that apply BDDs to design verification. Include your results in your pdf file.