Flipflops

FLIP FLOPS

·         A flip flop is a sequential loic device used to store one bit information. It is also called as bi-stable device since it has two possible states: 1 (high) and 0 (low).

Types of flip flops:

1.       RS flip flop.

2.       Clocked RS flip flop.

3.       D flip flop

4.       J-K flip flop.

5.       T flip flop.

RS flip flop:

·         RS flip flop has two inputs labelled S and R. The two outputs are labelled Q and Q. In flip flops the outputs are always complementary. In other words, if output Q =1, then output Q=0, and so on. The letters R and S are often referred as set and reset inputs.

                                                

  Truth table

S	R	Q(n+1)	Comments
0	0	Qn	No change
0	1	0	Reset
1	0	1	Set
1	1	x	Not allowed

·        

A  high S (S=1) and low R (R=0) results in the set state (Q=1).

·         A low S (S=0) and high R (R=1) results in the reset state (Q=0).

·         When both inputs are low (S=0, R=0), results in no change in output(Q= lastvalue).

·         When both inputs are high (S=1, R=1), results in indeterminate state and this is known as race condition.