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Monday, April 4, 2011

IMPLEMENTATION OF SHIFT REGISTERS


      IMPLEMENTATION OF SHIFT REGISTERS


AIM:                           

To implement and verify the truth table of a serial in serial out shift register.      

APPARATUS REQUIRED:

S.No
Name of the Apparatus
Range
Quantity
1.
Digital IC trainer kit

1
2.
D Flip Flop
IC 7474
2
3.
Connecting wires

As required

THEORY:

A register capable of shifting its binary information either to the left or to the right is called a shift register.  The logical configuration of a shift register consists of a chain of flip flops connected in cascade with the output of one flip flop connected to the input of the next flip flop.  All the flip flops receive a common clock pulse which causes the shift from one stage to the next.

The Q output of a D flip flop is connected to the D input of the flip flop to the left.  Each clock pulse shifts the contents of the register one bit position to the right.  The serial input determines, what goes into the right most flip flop during the shift.  The serial output is taken from the output of the left most flip flop prior to the application of a pulse.  Although this register shifts its contents to its left, if we turn the page upside down we find that the register shifts its contents to the right.  Thus a unidirectional shift register can function either as a shift right or a shift left register.

PIN DIAGRAM OF IC 7474:





CIRCUIT DIAGRAM:


TRUTH TABLE:

For a serial data input of 1101,

S.NO
CLOCK
PULSE
 INPUTS
OUTPUTS
D1
D2
D3
D4
Q1
Q2
Q3
Q4
1
1
1
X
X
X
1
X
X
X
2
2
1
1
X
X
1
1
X
X
3
3
0
1
1
X
0
1
1
X
4
4
1
0
1
1
1
0
1
1
5
5
X
1
0
1
X
1
0
1
6
6
X
X
1
0
1
X
1
0
7
7
X
X
X
1
0
X
X
1
8
8
X
X
X
X
X
X
X
X

PROCEDURE:

  1. Connections are given as per the circuit diagrams.
  2. Apply the input and verify the truth table of the counter.


RESULT:
The truth table of a serial in serial out left shift register was hence verified.

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