文档介绍：Combinational logic circuits
Chapter 3
Analysis & design
Definition of combinational logic
Let X be the set of all input variables , X={X0, X1, ……, Xn}
Let Y be the set of all output variables , Y={Y0, Y1, ……, Ym}
Y=F(X) >> Yi=F(X0, X1, ……, Xn)
The combinational function, F, operated on the input variable set X, to produce the output variable set Y.
The output is related to the input as
Combinational logic function (F)
X0
Xn
Y0
Ym
Definition of combinational logic
Logic circuits without the feedback from output to input
Logic circuits constructed from a functionally completely gate set, contain no memory unit
Combinational logic function (F)
X0
Xn
Y0
Ym
Analyze a combinational logic circuit
Function statement
Construct truth table
Simplify equation
Switching equation
Logic diagram
Convert logic diagram to switching equation
Simplify the expression
derive the truth table from the simplified switching equation
Give the pertinent statement of the circuit (function\design)
Design a combinational logic circuit
Logic circuit built
Logic diagram drawn
Equations simplified
switching equations written
Truth table Construction
Problem statement
Develop a proper statement of the problem
Based on the problem statement, construct truth table that clearly established the relationship between the input and output variables
Design a combinational logic circuit
Determine the input variables and output variables that are involved
Assign mnemonic or letter or number symbols to each variable
Determine the size of the truth table
Construct a truth table containing all of the input variable combination
By careful reading of the problem statement determine the combinations of input that cause a given output to be true
Truth table Construction
Problem statement
Elements
Two operator
Material
Interlock switch
Motor
put conveyor into action >> the motor is turning on
Either of two operators is in