CS 221 - Computer Logic and Organization

Shai Simonson    306 Stanger    (508) 565-1008

Email:  shai@stonehill.edu

Homepage: http://www.stonehill.edu/compsci/shai.htm

Assignment 2 - 35 points

Chapter 3 - Pages 92-97 - Due: Wednesday, October 11.

Problems: 1c, 2c, 3, 4c,d, 10, 12, 27, 28.  (points:  2, 3, 4, 4, 4, 3, 6, 4)

(Second Edition:  1c, 2c, 3 b,d, 4 c,d, 10, 12, 26, 27.  (points:  2, 3, 4, 4, 4, 3, 6, 4))

Notes on the book's notation:  The book sometimes uses "minterms" and "maxterms" to express Boolean formulas.  Minterms are products of Boolean variables and maxterms are sums.  Page 34 of your book explains the notation.  The sum of products is Sigma of minterms, and the product of sums is Pi of maxterms.  If you don't understand the "Sigma" and "Pi" notation please ask me. 

My Problem:   (5 points)

Design a circuit for this problem.  There are many ways to do this, from sheer brute force, to methods that use circuits we discussed including adders and multiplexers.

Given a 4-bit number x, output a BCD number (4 bits) equal to the units digit of x in base 10, and light up a "tens digit" single LED whenever the value of x is between 10 and 15 inclusive.  For example: if x = 1101 (13 in base 10), then the "tens" LED will be lit (1).  And the BCD units digit will be 0011 (3 in base 10). 

The idea is that you want to display a two digit number, the right digit is 7-segment display fed by a 4-bit BCD number, and the left digit is either 0 or 1, so it is represented by a single LED.  You do not need to design or draw the circuit to take the 4-bit BCD number and output the 7-segment display.  That circuit is in the book and not part of your problem.  Your part of the job is to take 4-bits and output 5 bits:  1 for the ten's digit LCD, and 4 for the BCD units digit.