22 March 2020

Counter Interview Question Answer - 4



46
What is reason behind the name ‘ Twisted ring counter ’?
           OR
How the Johnson counter is constructed?


Twisted ring counter
  • The twisted counter is constructed by using serial in serial out shift register.
  • The Q output of each stage is connected to the D input of the next stage but the output Q bar of the last stage is connected to the D input of the first stage therefore it is called as twisted ring counter.


47
How many states and pulses counted by n flip flop Johnson counter?
             OR
Why the Johnson counter is called as Mod – 2n counter?


Mod – 2n counter
  • An N flip flop Johnson counter can count up to 2n pulses and 2n unique states therefore it is called as mod – 2n counter.


48
Why the Johnson counter is lies between ring counter and ripple counter?


Johnson counter
  • The Johnson counter lies between ring counter and ripple counter because the Johnson counter requires more decoding circuit than that of ring counter whereas it requires less decoding circuit than by the ripple counter.


49
Which type of counter suffers from problem of lock out?


Ring counter and Johnson counter

50
How the problem of lock out can be corrected in the ring counter?


Lock out
  • The lock out problem in the ring counter is corrected by using adding AND gate.
  • If the counter find itself is in the unused state, the counter find its way to used state after number of clock pulses.


51
Describe the function of the pulse train generator.


Function of Pulse train generator
  • The function of the Pulse train generator is to generate prescribed sequence of logic bits.


52
Which type of logic is used for Pulse train generator?


Direct logic or indirect logic

53
Describe the advantage of Pulse train using indirect logic.


Advantage of Pulse train using Indirect Logic
  • The advantage of pulse train using indirect logic is that any counter with correct number of states can be formed by the pulse train generator.


54
How many numbers of flip flops require for N states pulse generation using shift registers?


The minimum number of flip flops require for N state pulse generation using shift register such that
   N < 2n
   N = Number of state and
   n = Number of flip flops

55
Describe the disadvantages of pulse generator using shift register.


It is very difficult to generate unique states by pulse generator using shift register.

56
Explain the term : Linear sequence generator


Linear sequence generator
  • It is a pulse sequence generator which can generate 2n – 1 unique state for n flip flops shift registers.
  • It will generate all states except zero state.


57
How many unique states that can be generated by linear sequence by using n flip flop shift register?


2n – 1

58
Explain : Full modulus cascading


Full modulus cascading
  • The cascading of counter is full modulus if the overall modulus is the product of the individual moduli of all the cascaded counters.


59
Write the applications of the counters?


Applications of counters
  • Frequency counter
  • Parallel to serial data conversion
  • Digital clock


60
How the pulse generated by using shift registers?


Pulse generator
  • There are N flip flops are connected in cascade similar to that of in a shift register.
  • The clock pulse is applied to each flip flop.
  • The output of the each flip flop is connected to input D of the first flip flop via combinational logic circuit.
  • The prescribed sequence of pulse appears at the output of the each flip flop.


61
Which condition must be satisfied for sequence generator generates a sequence of length L using n flip flops?  


L ≤ 2n – 1


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