COMBINATIONAL LOGIC ANALYSIS

Chapter 5 COMBINATIONAL LOGIC ANALYSIS

Combination of basic gates to form circuits that can carry out a desired application. • In combinational logic, the output level is at all times dependent on the combination of input levels • Combinational logic circuits contain no memory (no ability to store information) DEFINITION OF COMBINATIONAL LOGIC

AND-OR LOGIC • Represents SOP implementation – AND gate for product term, OR gate for summing the product terms

AND-OR-INVERT LOGIC • Represents POS implementation – AND gate for product term, OR gate for summing the product terms, NOT gate to complement the AND-OR circuit

XOR LOGIC • Combination of 2 AND gates, 1 OR gate, & 2 NOT gates. • Considered a type of logic with own unique symbol ( ).

XNOR LOGIC • The complement of XOR logic.

Implement logic circuit fromBoolean Expression • Example: Logic circuit for X = AB + CDE

Draw logic circuit for X = AB(CD + EF) Exercise 1

Implement logic circuit fromTruth-table • First, write the SOP expression from the Truth Table. Then, implement the logic circuit.

NAND gate is a universal gate because it can be used to produce the NOT, AND, OR and NOR functions. Universal Gate

Universal Gate

NOR gate is also a universal gate because it can be used to produce the NOT, AND, OR and NAND functions. Universal Gate

Universal Gate

NAND NEGATIVE OR

NOR NEGATIVE AND

The output of a logic circuit at any given time depends on the input at that particular time. • Example: Determine the final output waveform X for the circuit in figure below, with input waveforms A,B and C as shown.

COMBINATIONAL LOGIC ANALYSIS