SEQUENTIAL CIRCUIT
1. A sequential
circuit is a circuit in which the output will depend on both present input and
previous input
2. The
block diagram for sequential circuit is shown below
3. In sequential circuit there are two
blocks. They are:
1. Combinational
circuit
2. Memory
elements
4. The memory elements are devices which
are used to store binary information.
5. The binary elements stored in memory
elements at any given time define the state of sequential circuit.
6. There are two types of sequential
circuits. They are:
1. Synchronous
sequential circuit
2. Asynchronous
sequential circuit
7. A
Synchronous sequential circuit is a system whose behavior can be defined
from the knowledge of signals at discrete instant of time.
8. Asynchronous sequential circuit depends
on the order in which the input signal change and can be effected at any
instant of time.
9. Generally the synchronous sequential
circuit that uses clock pulses as the input of memory elements is known as
CLOCKED SEQUENTIAL CIRCUIT.
10.The memory elements used in clocked
sequential circuit are known as FLIP- FLOP.
11.The circuits are
capable of storing one bit of information.
FLIP-FLOPS
·
A flip-flop circuit can maintain the
binary state indefinitely, until the input signal switches to another state.
·
A flip-flop circuit has the output in
which one output is present in normal form and another output is present in
compliment form.
·
There are different types of flip-flops.
The difference between various types of flip-flops is in the number of input
values.
·
A flip-flop can be designed by using
NAND gate and NOR gate.
·
The
basic flip-flop circuit using NAND gate and NOR gate is as shown below.
·
By using the basic flip flop we can
design different types of flip flop
·
In basic flip flop the connection
between two gates is known as “Crossed Couple”
·
Crossed couple means the output of one
gate is given as the input of the second gate.
·
In flip flop there are two inputs. They
are S for Set and R for Reset.
·
For flip flop there are two outputs.
They are Q and Q’.
·
Here one of the output is present in
normal form and another output is present in compliment form
·
This type of flip flop is known as
“Direct Coupled RS Flip flop”.
RS FLIP FLOP