4-bit Johnson counter

Johnson counter:

The shift or twisted-ring counter or switch-tail ring counter is constructed similar to a standard ring counter except that the inverted output of the last flip-flop is connected to the input of the first flip-flop. This counter is also known as the Johnson Counter.

From the truth table, one can observe that for a 4-bit shift counter, there are 8 states. In general, an n-flip-flop shift counter will result in 2n states or a Modulo-2n counter.