List the eight unused states in the switch-tail ring counter of Fig. 6.18 (a). Determine...

List the eight unused states in the switch-tail ring counter of Fig. 6.18 (a). Determine the next state for each of these states and show that, if the counter finds itself in an invalid state, it does not return to a valid state. Modify the circuit as recommended in the text and show that the counter produces the same sequence of states and that the circuit reaches a valid state from any one of the unused states.