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Outline

How do we simplify logic functions?

Abstract

 Boolean approach  An SOP is minimized if uses fewest implicants  (same implicants -> fewer literals)  Prime implicant cannot be combined to form a new implicant with fewer literals  Implicants in a minimal equation must be all prime  Example: minimize NOR Simplification  Trial and error process  Importance  Smaller, cheaper, possibly faster circuits

Plan for the week Copyright © 2016 Elsevier Ltd. All rights reserved. Simplifying equations  Boolean approach  An SOP is minimized if uses fewest implicants  (same implicants -> fewer literals)  Prime implicant cannot be combined to form a new implicant with fewer literals  Implicants in a minimal equation must be all prime  Example: minimize Copyright © 2016 Elsevier Ltd. All rights reserved. Schematics PLA form Copyright © 2016 Elsevier Ltd. All rights reserved. Schematics  Wires connections Copyright © 2016 Elsevier Ltd. All rights reserved.  One way Copyright © 2016 Elsevier Ltd. All rights reserved.  Another way Copyright © 2016 Elsevier Ltd. All rights reserved. Schematics Simplification of to Copyright © 2016 Elsevier Ltd. All rights reserved. Schematics  Further simplification NOR Copyright © 2016 Elsevier Ltd. All rights reserved. Simplification  Trial and error process  Importance  Smaller, cheaper, possibly faster circuits Copyright © 2016 Elsevier Ltd. All rights reserved. Karnaugh maps Copyright © 2016 Elsevier Ltd. All rights reserved. Basics  Graphical method  Good up to 4 variables  Combinable terms are next to each other Copyright © 2016 Elsevier Ltd. All rights reserved. K-maps  2 inputs A B Y B 0 0 1 A 0 1 0 1 1 0 1 1 1 0 0 1 0 0 1 1 0  Square of k-map = row Truth table  Square of k-map = minterm  Adjacent squares differ in one variable minterms K-maps  Adjacent squares differ in one variable  Gray code  Wraps around Copyright © 2016 Elsevier Ltd. All rights reserved. Function  Circle 1’s  Write implicant for circles  Variables with true and complementary form are excluded from implicant Copyright © 2016 Elsevier Ltd. All rights reserved. Minimization  Circle all rectangular blocks of 1’s using the fewest possible number of circles  Each circle is an implicant  Largest circles are prime implicants Copyright © 2016 Elsevier Ltd. All rights reserved. Minimization  Rules  Fewest circles  All squares in a circle are 1’s  Each circle -> rectangular block power of 2  Each circle as large as possible  Can wrap around  1 may be circled multiple times Copyright © 2016 Elsevier Ltd. All rights reserved. Minimization Copyright © 2016 Elsevier Ltd. All rights reserved. Figure 2.46 Solution for Example 2.9 Copyright © 2016 Elsevier Ltd. All rights reserved. Example: 7 segment decoder Copyright © 2016 Elsevier Ltd. All rights reserved. Figure 2.48 Seven-segment display digits Copyright © 2016 Elsevier Ltd. All rights reserved. Figure 2.49 Karnaugh maps for Sa and Sb Copyright © 2016 Elsevier Ltd. All rights reserved. Figure 2.50 K-map solution for Example 2.10 Copyright © 2016 Elsevier Ltd. All rights reserved. Figure 2.51 Alternative K-map for Sa showing different set of prime implicants Copyright © 2016 Elsevier Ltd. All rights reserved. Figure 2.52 Alternative K-map for Sa showing incorrect nonprime implicant Copyright © 2016 Elsevier Ltd. All rights reserved. Don’t care  Variables that do not affect output  Can be 0 or 1 Copyright © 2016 Elsevier Ltd. All rights reserved.
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Universidad Nacional del Sur, Faculty Member

I am also "Investigador Principal" at CONICET

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