13.21.1.1 Start-up Sequence

When the motor being driven is at rest, the BEMF voltage is equal to zero. The motor needs to be rotating for the BEMF sensor to lock onto the rotor position and commutate the motor. The recommended start-up sequence is to bring the rotor from rest, up to a speed fast enough to allow BEMF sensing. Motor operation is comprised of five modes: Disabled mode, Bootstrap mode, Lock or Align mode, Ramp mode and Run mode. Refer to the commutation state machine in Table 13-6. The order in which the host dsPIC DSC steps through the commutation state machine determines the direction that the motor rotates.