US Patent 7106019 Digital communication link

A serial interface circuit electrically connected to a controller to control an electric motor. The interface circuit includes a controller circuit and a motor circuit. The controller circuit includes a transmitter and a receiver circuit, and the motor circuit includes a transmitter circuit and a receiver circuit. The interface interrogates the motor to acquire status and diagnostic information by receiving commands from the controller, adjusts a voltage level to a desired level, outputs the voltage signal to command and control the motor, and receives a voltage response from the motor.