Design a sequential circuit to control the motor of a tape player. The logic circuit will have five inputs and three outputs. Four of the inputs are the control buttons on the tape player. The input PL is 1 if the play button is pressed, the input RE is 1 if the rewind button is pressed, the input FF is 1 if the fast-forward button is pressed, and the input ST is 1 if the stop button is pressed. The fifth input to the control circuit is M, which is 1 if the special “music sensor” detects music at the current tape position. The three outputs of the control circuit are P, R, and F, which make the tape play, rewind, and fast forward, respectively, when 1. No more than one output should ever be on at a time; all outputs off causes the motor to stop. The buttons control the tape as follows: If the play button is pressed, the tape player will start playing the tape (output P = 1). If the play button is held down and the rewind button is pressed and released, the tape player will rewind to the beginning of the current song (output R = 1 until M = 0) and then start playing. If the play button is held down and the fast forward button is pressed and released, the tape player will fast forward to the end of the current song (output F = 1 until M = 0) and then start playing. If rewind or fast forward is pressed while play is released, the tape player will rewind or fast forward the tape. Pressing the stop button at any time should stop the tape player motor.
(a) Construct a state graph chart for the tape player controller. You may assume that only one of the four buttons can be pressed at any given time.
(b) Write Verilog code for the controller.