DIGITAL ELECCTRONICS

State Diagram

&

Characteristics Eq. of Sequential Circuit

PREET|patel (151310109032)

2nd Year B.E. Electrical

AIIE

CONTENTS:

• INTRODUCTION

• JK FLIP FLOP

• D FLIP FLOP

• SR FLIP FLOP

• T FLIP FLOP

• Conversion from SR FF to T FF

INTRODUCTION

• We use the truth table for explaining the relation between its inputs and outputs of a circuit

combinational.

• But the use of truth table is not suitable for explaining the input output relation for a sequential

circuit.

• Instead we use the STATE TABLE for the sequential circuits. The basic building block of a sequential

circuit is a flip flop. The outputs QA, QB etc. of such flip flops will be used as state inputs to a

sequential circuit. They are also called as state variable.

• In addition to this "x" represents an external input and Y represents the output of the sequential

circuit.

• Y will be dependent on the state variables and the external input x.

JK FLIP FLOP

Truth table

JK FLIP FLOP

P.S N.SI/P

S0 S1

0/0

0/1 0/X

QN J K QN

0 0 X 0

0 1 X 1

1 X 1 0

1 X 0 1

Excitation table

STATE EQUATION

• State equation is the combination of P.S and I/P to the flip-flop.

STATE Equation JK flip flopQn+1 = QnJ + QnK

D FLIP-FLOP

CHRACHTERISTIC TABLE

D QT QT+1

0 0 0

0 1 0

1 0 1

1 1 1

D

CLK

STATE EQUATION

• State equation is for D FLIP-FLOP is given by :

QT+1= DQ + DQQT+1 = D

SR FLIP-FLOP

CHRACHTERISTIC TABLE

QN S R QN

0 0 X 0

0 1 0 1

1 0 1 0

1 X 0 1

T-FLIP FLOP

CHRACHTERISTIC TABLE

T QT QT+1

0 0 0

1 0 1

1 1 0

0 1 1

CONVERSION FROM SR FF TO T FF

INPUT OUTPUTS

T P.S Qn N.S Qn+1 S R

0 0 0 0 X

1 0 1 1 0

1 1 0 0 1

0 1 1 X 0

0 X

1 0

X 0

0 1

TQn

TQn

S=TQn R=TQn

THANK YOU