Ring Counter in Digital Electronics

Ring counter is a synchronous counter since all the flip flops are clocked simultaneously. A ring counter is a circular shift register with only one flip flop being set at any particular time, all others are cleared. The single bit is shifted from one flip flop to the other to produce the sequence of timing signals.

Ring counter in digital electronicsIt is a 4-bit shift register connected as a ring counter. In this counter, Serial In Da is connected to Serial Out Qd.

First of all, CLR’ is set to 0 to clear all flip flops and then it is set to 1 for the circuit operation. After clearing all the flip flops, Pr’ of 4th flip flop is set to 0 while for all other three flip flops, it set to 1. This is done so that the initial value of register becomes 0001 [Pr’=0, sets the 4th flip flop to 1].

Single bit is shifted right with every clock pulse. Each flip flop is in 1 state once every four clock pulses.

CLK Qa Qb Qc Qd
0 0 0 0 0
0 0 0 0 1
1 1 0 0 0
2 0 1 0 0
3 0 0 1 0
4 0 0 0 1

Disadvantages of Ring Counter

  1. Using ring counter, one can count only four distinct states which is totally wastage of flip flops.
  2. Ring counter doesn’t count in a binary sequence so it is not preferred.

Mod of the Ring Counter is “n” where n is the number of flip flops. In a Ring Counter, the frequency of output is divided by n, therefore, it is known as divide by N counter.

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