Sunday, 2 December 2012

What is Flip-Flops|Explain S-R Flip-Flop


By on 02:06

Flip-Flop is a circuit which contains 2 outputs,one for normal value and other for opposite value or in simple words,it contains two states i.e. 0 and 1.

Type of Flip-Flop:-


1)S-R Flip-Flop

2)J-K Flip-Flop
3)D Flip Flop
4)T Flip-Flop

S-R Flip Flop:-


S-R stands for Set-Reset,in which reset means "clear".We can construct S-R flip flop with or without clock.In which '1'=Set and '0'=Reset.


Block Diagram of S-R flop flop:-



Truth Table:-


S R Q(n+1) Q(n+1)' Action
0 0 Q(n) Q(n)' No Change
0 1 01 Reset
1 0 10 Set
1 0 X X Forbidden

PS-NS Table(or Present State-Next State):-



Q(n) S R Q(n+1) Q(n+1)' Action
0 0 0l 0 1 No Change
0 0 1 0 1 Reset
0 1 0 1 0 Set
0 1 1 X X Forbidden
1 0 0 1 0 No change
1 0 1 0 1 Reset
1 1 0 1 0 Set
1 1 1 X X Forbidden

Excitation Table or Application Table:-



Q(n) Q(n+1) S R
0 0 0 X
0 1 1 0
1 0 0 1
1 1 X 0


Characteristic Equation of S-R flip flop:-

Q(n+1)=Q(n)'SR'+Q(n)R'

=R'(Q(n)S+Q(n))
=R'(Q(n)+s)
=Q(n)R'+SR'

Circuit Diagram of S-R flip flop using NAND gate:-





Circuit Diagram of S-R flip flop using NOR gate:-





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