This controller can be implemented by a sequential machine with three states. It requires a 3-bit register, N, and an incrementer to count through the eight add/shift steps. This controller goes from state 00 to state 01 when s 1 (and remains in state 00, otherwise). It goes from state 01 to 10 when register N contains three 1’s (and returns to state 01, otherwise). It always goes from state 10 to 00 on the next clock. The design of the sequential circuit is left as an exercise.