Question

To operate correctly, starting a ring shift counter requires __________

(a) Clearing all the flip-flops

(b) Presetting one flip-flop and clearing all others

(c) Clearing one flip-flop and presetting all others

(d) Presetting all the flip-flops

I had been asked this question at a job interview.

This question is from Universal Shift Registers topic in portion Registers of Digital Circuits

Answer 1

Correct choice is (b) Presetting one flip-flop and clearing all others

To elaborate: In Ring counter, the feedback of the output of the FF is fed to the same FF’s input. To operate correctly, starting a ring shift counter requires presetting one flip-flop and clearing all others so that it can shift to the next bit.