After detecting the initial position of the motor in motor startup stage, MCF83xx accelerates the motor in open loop, with speed reference at any given time determined by Equation 1. Open loop acceleration coefficients, A1 and A2 are configured through OL_ACC_A1 and OL_ACC_A2 respectively. The current limit in open loop is set by OL_ILIMIT. The motor speed is increased in open loop with peak value of the motor phase current limited to OL_ILIMIT. The function of the open-loop operation is to drive the motor to a speed at which the motor generates sufficient BEMF to allow the back-EMF observer to accurately detect the position of the rotor.

Once the motor has reached a sufficient speed for the back-EMF observer to estimate the angle and speed of the motor, the MCF83xx transitions into closed loop state. The transition from open loop to close loop is referred as handoff, and the speed at which this transition happens is referred as handoff speed. The handoff speed is automatically determined based on the measured back-EMF and motor speed if AUTO_HANDOFF_EN is set to 1b. Users also have an option to manually set the handoff speed by configuring OPN_CL_HANDOFF_THR and setting AUTO_HANDOFF_EN to 0b. The theta error (Ɵgen - Ɵest) at handoff point is decreased linearly after transition with ramp rate configured by THETA_ERROR_RAMP_RATE, for a smooth transition to closed loop and to avoid speed transients.