Combination circuit characteristic combination logic circuit structure introduction

1 combination circuit is a circuit composed of logic gate (represented digital device) and electronic components, there is no feedback in the circuit, no memory component;

The output state of the 2 combination circuit at any time depends only on the state combination of each input at that time, and is independent of the time variable.

Combinational logic circuit structure

Combinational logic circuit: The output state at any one time depends only on the digital circuit of each input state combination at that time.

Known by the truth table, the circuit converts the input binary code A3A2A1 to output the cyclic code Y3 Y2 Y1. That is, at any time, a set of binary codes is input, and the output is the cyclic code corresponding to the group code, regardless of the time variable.

Combination circuit characteristics Combination logic circuit structure introduction

Analysis of combinatorial logic

Analysis of combinatorial logic: Find the logic function of the output function from a given logic diagram. That is, the logical expression and the truth table are obtained.

The steps are generally:

(1) Deriving the logical expression of the output function of the logic circuit and simplifying it.

First, the output of each gate in the logic diagram is marked with letters, and then the output function of each gate is derived step by step from the input stage.

(2) Establish a truth table from a logical expression

The method of making a truth table is to first list all combinations of input signals, and then substitute each combination into an output function to obtain an output signal value.

(3) Analyze the truth table to judge the function of the logic circuit

Try to analyze the function of the logic diagram shown in the figure.

Combination circuit characteristics Combination logic circuit structure introduction

Legend circuit diagram

Solution: (1) Write logic function and simplify according to logic diagram

Combination circuit characteristics Combination logic circuit structure introduction

(2) The column truth table is as shown in the table.

(3) Analysis logic function

From the truth table:

Combination circuit characteristics Combination logic circuit structure introduction

When A and B are the same, Y=1, A, B, and Y=0 when they are different, so the circuit is the same or logic circuit.

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