Spindle motor initialization after a control processor reset condition in a disc drive

A disc drive, comprising:

• a spindle motor configured to rotate at least one recording disc;
• a read/write bead configured to write data to the disc and read data from the disc;
• back electromotive force (bemf) detection circuitry coupled to the spindle motor and which detects bemf from rotation of the spindle motor above an intermediate velocity;
• commutation circuitry coupled to the bemf detection circuitry and spindle motor which electrically commutates the spindle motor in relation to the detected bemf over a range of electrical rotational positions of the spindle motor;
• and
• a control circuit which, upon initialization of the disc drive, determines the presence or absence of detected bemf from the bemf detection circuitry, and in the absence of detected bemf sequentially identifies the electrical rotational position of the spindle motor, directs the application of a braking force to the spindle motor, determines whether the spindle motor is rotating in relation to a change in the electrical rotational position of the spindle motor, and commands an acceleration of the spindle motor to a final, operational velocity by the commutation circuitry when the spindle motor is determined to be at rest, wherein the final, operational velocity is a velocity at which user data are read from the disc and transferred to a host device.

A disc chive, comprising:

• a spindle motor configured to rotate at least one recording disc;
• a read/write head configured to write data to the disc and read data from the disc;
• back electromotive force (bemf) detection circuitry coupled to the spindle motor and which detects bemf from rotation of the spindle motor above an intermediate velocity;
• commutation circuitry coupled to the bemf detection circuitry and spindle motor which electrically commutates the spindle motor in relation to the detected bemf over a range of electrical rotational positions of the spindle motor;
• and
• means for initializing the disc drive to bring the spindle motor to a final, operational rotational velocity at which user data are transferred between the disc and a host device alter determining that the spindle motor is either at rest or rotating at a rotational velocity less than the intermediate velocity due to an absence of detected bemf from the spindle motor, by identifying the electrical rotational position of the spindle motor, applying a braking force to the spindle motor, and detecting a change in the electrical rotational position of spindle motor after application of the braking force.

A method, comprising:

• detecting an absence of sensed rotation from a motor;
• sequentially identifying a first electrical rotational position of the motor, applying a braking force to the motor and identifying a second electrical rotational position of the motor;
• and
• determining the motor to be in the stopped condition or in the low speed rotation condition in relation to the first and second electrical rotational positions.