Servo control apparatus

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG.
1 illustrates a data storage medium 10 and a servo control apparatus or circuit 12 for use in relation to the storage medium 10.
While the principles of the present invention can be applied to a number of different data storage media, as one example the storage medium 10 is a rotatable disk 14 having a data storage surface 16.
A plurality of concentric tracks 18 for storing data are on the data surface 16, together with a sector 20 that stores servo data for each of the tracks 18 in accordance with the present invention, as will be further described.
The servo control circuit 12 includes a recording head 22 coupled to a conventional read/write control circuit 24 via a line 26 for reading or writing data.
Control circuit 24 controls recording head 22 to read or write data on data surface 16 in response to conventional write data, write gate and read data control signals received on line 28, line 30 and line 32, respectively.
When reading the servo data stored in sector 20 on surface 16, the outputs of control circuit 24 are digital data on a line 34 representing the servo data being read and a digital DC threshold signal on a line 36 indicating that, for example, data and not noise are being read.
A servo demodulator 38 has a data input and a threshold signal input connected, respectively, to output line 34 and line 36 of the read/write control circuit 24.
As will be further described, servo demodulator 38 demodulates the servo data stored in sector 20 on a given track 18 and produces digital data on output lines shown generally at 40 that have information about the position of recording head 22 relative to the center of the given track 18.
A controllable circuit 42 for controlling the radial position of recording head 22 across data surface 16 includes a microstep control motor 44 connected to a head positioner 46 via control lines shown generally at 48.
A data processor 50, such as a programmable microcomputer or microprocessor 52, responds to the digital data on line 40 by generating microstep control STATES on output lines shown generally at 54 that control the energization of motor 44