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.
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