Microprocessor controlled rigid disk file subsystem

An electrical control circuit for a miniature fixed disk drive subsystem, the subsystem including a head and disk assembly including an enclosed housing, a plurality of rotating disks at least one of which is a data storage disk, the disks having diameters not substantially greater than 95 millimeters and a plurality of positionable heads, there being one head associated with each data storage surface of the data storage disk, voice coil actuator means for positioning the heads at selected data storage tracks of a mulitplicity of such tracks concentrically defined on the data storage surfaces, the control circuit being directly connected to the head and disk assembly and comprising:

• head positioning means connected to control operation of the voice coil actuator means and including at least one servo loop for controlling the position of the head positioning mechanism of said assembly relative to the disks to cause the heads of said mechanism to move to a commanded track during track seeking operations and to cause said head to remain in substantial alignment with said commanded track during track following operations, the servo loop of the control means including head position sensing means for generating a normal signal and a signal in quadrature with the normal signal wherein recurrences of the normal signal and the signal in quadrature define the location of the data tracks of the data storage surfaces during track following operations and further characterize the track boundaries during head movements toward or away from a center of the disks during track seeking operations,
• interface means for receiving commands and data to be stored from a host computer directly via connection paths to at least one of the host computer's address, data and control buses and for sending the commands to a single microprocessor of the control circuit and for sending the data to be stored to a buffer memory of the control circuit and for returning subsystem status values from the single microrocessor and the data retrieved from the disk to the host computer,
• memory controller means for generating byte addresses for the said buffer memory to enable data to be written into the buffer memory and read out thereof,
• data sequencer state machine means including a read/write channel for controlling the sequencing of storage and retrieval of data between said surface and said buffer memory via said read/write channel and said head,
• the single programmed control microprocessor of the control circuit being operatively connected to the head positioning means and to the interface means, memory controller means and data sequencer for operatively controlling user data storage to the disk and retrieval of user data from the disk operations of said subsystem by supplying seek commands to the head positioning means in response to commands from the host computer to cause said head positioning means to move the heads to a selected track during track seeking and to maintain the heads in registration therewith during track following via the voice coil actuator means, by commanding the data sequencer state machine means an memory controller means to initiate transfer of user data blocks to and from a selected data surface via a selected head, buffer memory means and interface means and by reporting subsystem status to the host computer via the interface means.