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CPRE 281  Practice questions for exam #1
9/24/07
1.
Give a truth table for each of the following logic expressions:
(a) (X+Y)(X’+Y)
(b) XY’+YZ’+ZX’
2.
For each of the expression in question 1, draw the circuit using the logic gate
symbols.
3.
For the logic expression in question 1 (a),
(a) derive the canonical sumofproducts expression.
(b) derive the canonical productofsums expression.
4.
A 2variable comparator circuit receives four input signals P1, P0, Q1, Q0 and
produces an output signal F. The output F is 1 if
either (i) P1>Q1 or (ii) P1=Q1 and
P0 > Q0.
(a) Write the truth table for the output function F.
(b) Write the canonical SOP expression for F. Do not use shorthand notation.
(c) Write the canonical SOP expression for F in shorthand notation.
(d) Write the canonical POS expression for F. Do not use shorthand notation.
(e) Write the canonical POS expression for F in shorthand notation.
(f) Write the simplest logic expression for F by the Karnaugh map using SOP form.
(g) Write the simplest logic expression for F by the Karnaugh map using POS form.
(h) Let the cost of an expression be the total number of gates plus the total number of
inputs of the circuit implementing the expression. Assume that AND gates and
OR gates of any number of inputs are used in the implementation. NOT gates to
complement the input variables are also counted. What is the cost of the
expressions in (f) and (g)?
5.
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This note was uploaded on 04/06/2008 for the course CPR E 281 taught by Professor Chu,chris during the Fall '07 term at Iowa State.
 Fall '07
 chu,chris

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