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# SEQUENTIAL AND COMBINATIONAL CIRCUITS,DIGITAL LOGIC DESIGN

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COMBINATIONAL AND SEQUENTIAL CIRCUITS,DESIGN AND ANALYSIS PROCEDURE OF COMBINATIONAL CIRCUITS,

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### SEQUENTIAL AND COMBINATIONAL CIRCUITS,DIGITAL LOGIC DESIGN

1. 1. DIGITAL LOGIC CIRCUITS~ INTRODUCTION TO COMBINATIONAL ANDSEQUENTIAL CIRCUITS.~DESIGN PROCEDURE OF COMBINATIONALCIRCUITS~ANALYSIS PROCEDURE OF COMBINATIONALCIRCUITSPRESENTED BY:QURATULAINBS(CS)-1QUAID-E-AZAM UNIVERSITYISLAMABAD ,PAKISTAN.
2. 2. TYPES OF DIGITAL LOGICCIRCUITS COMBINATIONAL CIRCUITS SEQUENTIAL CIRCUITS
3. 3. COMBINATIONAL CIRCUITS Combinational Circuits are made of logicgates. Doesn’t contain memory element , that’swhy they cant store any information. Value of present output is determined bypresent input. Examples of combinational circuits arehalf adders, full adders, sub tractors etc.
4. 4. BLOCK DIAGRAM OF ACOMBINATIONAL CIRCUIT
5. 5. SEQUENTIAL LOGIC CIRCUITS Made up of combinational circuits andmemory elements. These memory elements are devicescapable of storing ONE-BIT information. Output depend on input and previousstate. Examples of sequential circuits are flipflops, counters, shift registers
6. 6. BLOCK DIAGRAM OF ASEQUENTIAL CIRCUIT
7. 7. TYPES OF SEQUENTIALCIRCUITSSequential circuits are of two types:1.SYNCHRONOUS CIRCUITS: In synchronous sequential circuits, the stateof the device changes only at discrete timesin response to a clock Pulse.2.ASYNCHRONOUS CIRCUITS: Asynchronous circuit is not synchronized bya clock signal; the outputs of the circuitchange directly in response to changes inInputs.
8. 8. DESIGN PROCEDURE OFCOMBINATIONAL CIRCUITSThis procedure involves the followingsteps: The problem is stated. The number of available inputvariables and output variables isdetermined. The input and output variables areassigned letter symbols. Truth table is drawn Boolean function for output is obtained.
9. 9. ANALYSIS PROCEDURE OFCOMBINATIONAL CIRCUIT TO DETERMINE THE OUTPUT FUNCTIONSAS ALGEBRAIC EXPRESSIONS. It is the reverse process of design procedure. Logic diagram of the circuit is given. Obtain the truth table from the diagram. Obtain Boolean function from the Truth Tablefor output.
10. 10. LOGIC DIAGRAM FORANALYSIS EXAMPLE:
11. 11. THE CIRCUIT HAS THREEINPUTS, A,B,CAND TWO OUTPUTS F1 AND F2 The Boolean function for outputs are:F2=AB+AC+BCT1=A+B+CT2=ABC Outputs functions for gates are :T3=F2’T1F1=T3+T2
12. 12. Substituting and simplifying, we get :
13. 13. TRUTH TABLE DRAWN FROMTHE LOGIC DIAGRAM.
14. 14. BOOLEAN FUNCTIONSOBTAINED FOR OUTPUT ARE : F2=AB+AC+BC F1=A’BC’+A’B’C+AB’C’+ABC
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