Abstract: Apparatus, methods, and systems can be employed for calibrating servos, and in some implementations, spiral servos are calibrated for use in self-servo-write (SSW) processes. In an aspect, an apparatus includes a timing reference detector configured to determine timing reference information from a back electromotive force signal associated with a rotating machine readable medium, and a servo track window period generator configured to determine a relative location of a spiral on the rotating machine readable medium based on the timing reference information.

Abstract: Methods, systems, and apparatus, including computer program products are described for calibrating servos, and in some implementations, calibrating spiral servos for use in self-servo-write (SSW) processes. In one aspect, a method is provided that includes determining timing reference information on a machine readable medium, locking a clock signal to the timing reference information, detecting a spiral on the machine readable medium, determining a location of the spiral using the clock signal, and calibrating a spiral servo according to the location of the spiral.

Abstract: Methods, systems, and apparatus, including computer program products are described for calibrating servos, and in some implementations, calibrating spiral servos for use in self-servo-write (SSW) processes. In one aspect, a method is provided that includes determining timing reference information on a machine readable medium, locking a clock signal to the timing reference information, detecting a spiral on the machine readable medium, determining a location of the spiral using the clock signal, and calibrating a spiral servo according to the location of the spiral.

Abstract: Information indicative of the placement of spindle motor components may be obtained and used to provide a correction to one or more BEMF-derived attributes used to control the spindle speed. In some implementations, first and second signals indicative of BEMF of different stator windings may be used to determine a speed-related characteristic. The speed related characteristic may be used to determine an error amount, which may be used to determine a correction factor to control the speed of the spindle motor.

Abstract: Methods, systems, and apparatus, including computer program products are described for calibrating servos, and in some implementations, calibrating spiral servos for use in self-servo-write SSW processes. In one aspect, a method is provide that includes rotating a machine readable medium, and detecting a spiral on the machine readable medium. Detecting a spiral on the machine readable medium includes detecting magnitudes of the spiral and a timing mark, storing a timestamp from a clock signal that corresponds to the timing mark of the spiral, determining a peak of the spiral from the magnitudes, and locking the clock signal to the peak of the spiral using the timestamp.

Abstract: Information indicative of the placement of spindle motor components may be obtained and used to provide a correction to one or more BEMF-derived attributes used to control the spindle speed. In some implementations, first and second signals indicative of BEMF of different stator windings may be used to determine a speed-related characteristic. The speed related characteristic may be used to determine an error amount, which may be used to determine a correction factor to control the speed of the spindle motor.

Abstract: Information indicative of the placement of spindle motor components may be obtained and used to provide a correction to one or more BEMF-derived attributes used to control the spindle speed. In some implementations, first and second signals indicative of BEMF of different stator windings may be used to determine a speed-related characteristic. The speed related characteristic may be used to determine an error amount, which may be used to determine a correction factor to control the speed of the spindle motor.