Explain how a shift register can be used as a ring counter giving the wave forms at the output of the flipflops.

Ans:

Shift Register as a Ring Counter: A Ring Counter is a Circular Shift Register along with only one flip-flop being set at any exacting time; all other are cleared. The particular bit is shifted from one flip-flop to another to produce the sequence of timing signals. Fig.(a) demonstrates a 4-bit shift register linked as a ring counter. The initial value of the register is 1000, that produces the variable T₀. The single bit is shifted right along with every clock pulse and circulates back from T₃ to T₀. Each flip-flop is in the 1 state once all four clocks pulses and generates one of the four timing signals demonstrates in Fig.(b). All output becomes 1 after the negative-edge transition of a clock pulse and keeps 1 during the next clock pulse.

Fig.(a) 4-bit shift register connected as a ring counter.

Fig.(b) Waveforms at the output of Flip-Flops