Sensor-based control of a Three Phase Brushless DC Motor with Hall Sensors.
these motors are common in floppy disk drives and some hard disk drives. In this example the hall sensors are located on the far left and indicate the polarity of the armature above the stator.
The U, V, W phases have three states each: high, low, and floating. As each hall sensor changes state, logic controls the fets to switch the phase high (source current), low (sink current), or off (block current)
found all of this from atmel:
http://www.atmel.com/images/atmel-2596-sensor-based-control-of-three-phase-brushless-dc-motors_application-note_avr443.pdf
