Shift registers allow storing and transferring multiple bits of data using multiple flip-flops. There are four main types of shift registers: 1. Serial-in serial-out (SISO) registers allow serial input and output of data one bit at a time. 2. Serial-in parallel-out (SIPO) registers allow serial input but parallel output of all stored bits. 3. Parallel-in serial-out (PISO) registers allow parallel input but serial output of data one bit at a time. 4. Parallel-in parallel-out (PIPO) registers allow parallel input and output of all bits and act as a storage buffer.

1. Submitted by :- Umar Hassan Sofie
Reg. No:-UG1833001004
Submitted to :- prof. Gurwinder Singh
School of Engineering and Tchnology
B.Sc.(Computer Science) 3rd Semester
Digital Electronics(ECE301)

2. Shift Registers
Flip flops can be used to store a single bit , in order to store multiple bits we need
multiple flip flops. A Register is a device which is used to store such information. It is
a group of flip flops used to store multiple bits of data.
The information stored within these registers can be transferred with the help of shift
registers. The bits stored in such registers can be made to move within the registers
and in/out of the registers by applying clock pulses.

3. The registers which will shift the bits to left are called “Shift left registers”.
The registers which will shift the bits to right are called “Shift right registers”.
Shift registers are basically of 4 types. These are:
1.Serial In Serial Out shift register
2.Serial In parallel Out shift register
3.Parallel In Serial Out shift register
4.Parallel In parallel Out shift register
Types of registers

4. Serial-In Serial-Out Shift Register (SISO)
The shift register, which allows serial input (one bit after
the other through a single data line) and produces a serial
output is known as Serial-In Serial-Out shift register. Since
there is only one output, the data leaves the shift register
one bit at a time in a serial pattern, thus the name Serial-In
Serial-Out Shift Register.

5. Logic Diagram (SISO)
The logic circuit given below shows a serial-in serial-out shift register. The circuit consists of
four D flip-flops which are connected in a serial manner. All these flip-flops are synchronous
with each other since the same clock signal is applied to each flip flop.
The circuit is an example of shift right register, taking the serial data input from the left side
of the flip flop. The main use of a SISO is to act as a delay element.

6. Truth Table (SISO)

7. Waveform (SISO)

8. Serial-In Parallel-Out Shift Register (SIPO)
The shift register, which allows serial input (one bit after the other
through a single data line) and produces a parallel output is known
as Serial-In Parallel-Out shift register.

9. Logic Diagram (SIPO)
The circuit consists of four D flip-flops which are connected. The output of the first flip
flop is connected to the input of the next flip flop and so on.
All these flip-flops are synchronous with each other since the same clock signal is applied
to each flip flop.
The above circuit is an example of shift right register, taking the serial data input from the
left side of the flip flop and producing a parallel output.

10. Truth Table (SIPO)

11. Waveform (SIPO)

12. Parallel-In Serial-Out Shift Register (PISO)
The shift register, which allows parallel input (data is given separately to
each flip flop and in a simultaneous manner) and produces a serial output
is known as Parallel-In Serial-Out shift register.

13. Logic Diagram (PISO)
In this register output of the one flipflop Is connected to the input of the next flipflop via
combinational circuit and perform shift/load mode operation.
All these flip-flops are synchronous with each other since the same clock signal is applied to
each flip flop.

14. Shift/𝐋𝐨𝐚𝐝 Mode Operation (PISO)
Load mode:-
By the load mode we have the parallel input of data in which we have enter or load
the data in each of the flip flops simultaneously i.e. in the following example
flipflop-0 has bit o, flipflop- 1 has bit-1, flipflop-2 has bit -2 and flipflop-3 has bit-
3. It can be achieve by providing logic 0 at the input.

15. Shift/𝐋𝐨𝐚𝐝 Mode Operation (PISO)
Shift mode:-
The second aim of serial output is achieve mode with this operation. It is
responsible for serial movement of data i.e. the data will go from flipflop- 0 to
flipflop- 1, flipflop- 1 to flipflop- 2, flipflop- 2 to flipflop- 3 and the data store in
flipflop -3 is act as serial output.
It can be achieve by providing logic 1 at the input.
1011
1101
→1011

16. Parallel-In Parallel-Out Shift Register(PIPO)
The shift register, which allows parallel input (data is given separately to each flip
flop and in a simultaneous manner) and also produces a parallel output is known as
Parallel-In parallel-Out shift register. It is also known as storage register or buffer
register

17. Logic Diagram (PIPO)
In this type of register, there are no interconnections between the individual flip-flops
since no serial shifting of the data is required. Data is given as input separately for each
flip flop and in the same way, output also collected individually from each flip flop.
A Parallel in Parallel out (PIPO) shift register is used as a temporary storage device
and like SISO Shift register it acts as a delay element.
All these flipflops are synchronous with each other as they are connected with
same clock signal.

18. Waveform (PIPO)
Buffer means what ever value is given as input we get same value
as output.