(a) A Mealy sequential circuit has one input (x) and one output (z)

Chapter 14, Problem 14.13

(choose chapter or problem)

(a) A Mealy sequential circuit has one input (x) and one output (z). z can be 1 when the fourth, eighth, twelfth, etc. inputs are present, and z = 1 if and only if the most recent input combined with the preceding three inputs was not a valid BCD encoding for a decimal digit; otherwise, z = 0. Assume the BCD digits are received most significant bit first. Derive a state table for the circuit. (Eight states are sufficient.)

(b) Repeat for a Moore circuit (i.e., z = 1 if and only if, after the fourth, eighth, twelfth, etc. inputs have been received, the previous four inputs were not a valid BCD digit). (Nine states are sufficient.)

(c) Is it possible for a Moore circuit to generate the correct output while the fourth input bit is present rather than after it has been received? Explain your answer.