What is a Johnson counter



Johnson counter connects the complement of the output of the last shift register to its input and circulates a stream of ones followed by zeros around the ring. For example, in a 4-register counter, the repeating pattern is: 0000, 1000, 1100, 1110, 1111, 0111, 0011, 0001, so on.
vlsi interview question-Re: What is a Johnson counter?

In a 4-bit Johnson counter How many unused states are present?

4-bit Johnson counter: 0000, 1000, 1100, 1110, 1111, 0111, 0011, 0001, 0000.
8 unused states are present.