Combinational Logic Circuits Chapter 2 Mano and Kime
Combinational Logic Circuits Binary Logic and Gates Boolean Algebra Standard Forms Map Simplification NAND and NOR Gates Exclusive-OR Gates Integrated Circuits
Digital Logic Gates *
Gates with More than Two Inputs
Combinational Logic Circuits Binary Logic and Gates Boolean Algebra Standard Forms Map Simplification NAND and NOR Gates Exclusive-OR Gates Integrated Circuits
Basic Identities of Boolean Algebra
Implementation of Boolean Function with Gates
Combinational Logic Circuits Binary Logic and Gates Boolean Algebra Standard Forms Map Simplification NAND and NOR Gates Exclusive-OR Gates Integrated Circuits
Minterms for Three Variables
Sum of Products Design X Y minterms 0 0 m0 = !X & !Y 0 1 m1 = !X & Y 1 0 m2 = X & !Y 1 1 m3 = X & Y
Sum of Products Design X Y Z Design an XOR gate m1 = !X & Y m2 = X & !Y Z = m1 + m2 = (!X & Y) + (X & !Y)
Sum of Products: Exclusive-OR !X & Y X & !Y Z = (!X & Y) + (X & !Y)
Maxterms for Three Variables
Product of Sums Design Maxterms: A maxterm is NOT a minterm maxterm M0 = NOT minterm m0 M0 = m0’ =(X’. Y’)’ = (X + Y)” = X + Y
Product of Sums Design X Y minterms maxterms 0 0 m0 = !X. !Y M0 = !m0 = X + Y 0 1 m1 = !X. Y M1 = !m1 = X + !Y 1 0 m2 = X. !Y M2 = !m2 = !X + Y 1 1 m3 = X. Y M3 = !m3 = !X + !Y
Product of Sums Design X Y Z Design an XOR gate Z is NOT minterm m0 AND it is NOT minterm m3
Product of Sums Design X Y Z Design an XOR gate M0 = X + Y M3 = !X + !Y Z = M0 & M3 = (X + Y) & (!X + !Y)
Product of Sums: Exclusive-OR
Three- Level and Two- Level Implementation
Combinational Logic Circuits Binary Logic and Gates Boolean Algebra Standard Forms Map Simplification NAND and NOR Gates Exclusive-OR Gates Integrated Circuits
Two-Variable Map
Three-Variable Map
Three- Variable Map: Flat and on a Cylinder to Show Adjacent Squares
Three-variable K-Maps X YZ F = !X & !Y + X & Z
Three-variable K-Maps X YZ F = !X & !Y & !Z + !X & !Y & Z + X & !Y & Z + X & Y & Z F = !X & !Y & (!Z + Z) + X & Z & (!Y + Y) = !X & !Y + X & Z
Three-variable K-Maps X YZ F = Y & !Z + X 1
Three-variable K-Maps X YZ F = !X & !Y + X & y + Z
Three-variable K-Maps X YZ F = X & Z + !X & !Z
Three-variable K-Maps X YZ F = Y + !Z
Three-variable K-Maps X YZ F = m0 + m2 + m5 + m7 = (0,2,5,7)
Four-Variable Map
Four-Variable Map: Flat and on a Torus to Show Adjacencies
Four-variable K-Maps WX YZ Each square is numbered in the above K-map
Four-variable K-Maps WX YZ F(W,X,Y,Z) = (2,4,5,6,7,9,13,14,15)
Four-variable K-Maps WX YZ F = !W & X + X & Y + !W & Y & !Z + W & !Y & Z
Combinational Logic Circuits Binary Logic and Gates Boolean Algebra Standard Forms Map Simplification NAND and NOR Gates Exclusive-OR Gates Integrated Circuits
Prime Implicants F = XY’Z + X’Z’ + X’Y Each product term is an implicant A product term that cannot have any of its variables removed and still imply the logic function is called a prime implicant.
Combinational Logic Circuits Binary Logic and Gates Boolean Algebra Standard Forms Map Simplification NAND and NOR Gates Exclusive-OR Gates Integrated Circuits
Digital Logic Gates >
>
Logical Operations with NAND Gates
Alternative Graphics Symbols for NAND and NOT Gates
Logical Operations with NOR Gates
Two Graphic Symbols for NOR Gate
Generalized De Morgan’s Theorem NOT all variables Change & to + and + to & NOT the result F = X & Y + X & Z + Y & Z F = !((!X + !Y) & (!X + !Z) & (!Y + !Z)) F = !(!(X & Y) & !(X & Z) & !(Y & Z))
NAND Gate
X Y X Z Y Z F F = X & Y + X & Z + Y & Z
Combinational Logic Circuits Binary Logic and Gates Boolean Algebra Standard Forms Map Simplification NAND and NOR Gates Exclusive-OR Gates Integrated Circuits
Exclusive-OR Gate XOR X Y Z Z = X $ Y X Y Z X $ 0 = X X $ 1 = !X X $ X = 0 X $ !X = 1 X $ !Y = !(X $ Y) !X $ Y = !(X $ Y) A $ B = B $ A (A $ B) $ C = A $ (B $ C) = A $ B $ C
Exclusive-OR Constructed with NAND gates X & (!X + !Y) + Y & (!X + !Y) = X & !X + X & !Y + Y & !X + Y & !Y = X & !Y + Y & !X = X & !Y + !X & Y = X $ Y
Parity Generation and Checking
Combinational Logic Circuits Binary Logic and Gates Boolean Algebra Standard Forms Map Simplification NAND and NOR Gates Exclusive-OR Gates Integrated Circuits
Fully Complementary CMOS Gate Structure and Examples An Integrated circuit (IC) is a silicon semiconductor crystal, containing the components for the digital gates. The various gates are connected on the chip to form the IC.