Shift registers are used for temporary storage and can store multiple bits. There are two types: serial load and parallel load. Serial load registers shift data in or out one bit at a time on each clock cycle, while parallel load registers allow loading/output of all bits simultaneously. Common applications of shift registers include ring counters, Johnson counters, and pseudo-random pattern generators. A ring counter shifts data through the register and back to the first stage, counting through a fixed number of states. A Johnson counter also shifts data through the stages but with the last stage complement fed back to first, allowing it to count through more states than a ring counter.

1. SHIFT REGISTERS
&
APPLICATIONS

2. Registers:
We can say that A register is an extension
of a flip-flop that can store multiple bits.
Registers are commonly used as
temporary storage in a processor.
They are faster and more convenient
than main memory.
More registers can help speed up
complex calculations.

3. This registers are of two types
1. Serial load
2. Parallel load
1. Serial load registers:

4. 2. Parallel load register:

5. Serial in serial out:
After each clock pulse data will enter
into the flip flop serially and the output of
the present flip flop is fed to the next after
the 2nd clock pulse and so on..

6. Serial in parallel out:
Same as in SISO after 4 clock pulses
data is loaded into the register and the data
will be available at the output after 4 clock
pulses where as in SISO the will be
available at the out put after 8 clock pulses.

7. Parallel in serial out:
It shows the PISO register where the
mode control is used. When mode is low the
data is clocked into the flip flop and the
data is shifted when the mode bit is high

8. Parallel in parallel out:
In PIPO registers the data will appear
immediately at the output after a single
clock pulse and there is no clock delay.
This PIPO register are also known as
general register because of no shifting
operation.

9. APPLICATIONS
 Pseudo random pattern generator
 Ring counter
 Johnson counter or twisted counter

10. Ring counter:
 Ring counter is a shift register in which
the output of the last flip flop is fed to the
input again.
 For every clock pulse the data shifted into
the next flip flop thus it can count only N
states.

12. Johnson counter
 The complement of the output of the last
stage is connected back to the D input of the
first stage.
 Also called the twisted-ring counter.
 Require fewer flip-flops than ring counters
but more flip-flops than binary counters.
 An n-bit Johnson counter cycles through 2n
states.
 Require more decoding circuitry than ring
counter but less than binary counters.

14. Pseudo random pattern generator
 It is a simple shift register where the
vacated bit of is filled with the exclusive-or
of last two bits in the shift register.
 By using this for a n bit shift register we
can generate 2^n patterns.
 This is very useful in test pattern
generation.

15. Pseudo random pattern generator

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