
Suppose you are designing a circuit to control a cellphone's ringer and
vibration motor. Whenever the phone needs to ring from an incoming call
(input ring), your circuit must either turn on the ringer (output ringer
= 1) or the motor (output motor = 1), but not both. If the phone is in
vibrate mode (input vibrate_mode = 1), turn on the motor. Otherwise, turn
on the ringer.

module TopModule (
  input ring,
  input vibrate_mode,
  output ringer,
  output motor
);

