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Browse Prior Art Database

Helical Data Track Access Control

IP.com Disclosure Number: IPCOM000077634D
Original Publication Date: 1972-Aug-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Tsui, F: AUTHOR [+2]

Abstract

The servo system for accessing helical tracks in a magnetic disk storage operates by evaluating signals from a helical servo track and the contents of a cylinder address register.

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Helical Data Track Access Control

The servo system for accessing helical tracks in a magnetic disk storage operates by evaluating signals from a helical servo track and the contents of a cylinder address register.

Helical servo track 1 is recorded on servo disk 2. Data are stored in a similar helical track 3 on data disk 4. Transducers 5, 6 are mounted on carriage 7 which is positioned by voice coil motor 8.

Data recorded on helical track 3 are addressed by "cylinders". A "cylinder" is defined as the portion between two adjacent intersection points 9, 10 of track 3 with the radius 11 in the direction of index slot 12. Cylinder address register (CAR) is used to indicate the current position of carriage 7.

The digital output of CAR is converted into an analog voltage and fed to summing circuit 13. As carriage 7 is moved continuously inward along the helical track, CAR is continually counted up and a staircase waveform is received by summing circuit 13.

Bipolar servo signals, sensed by servo transducer 6, are converted to unipolar signals by clipping. These signals together with the pulses sensed by index slot transducer 15 from disk 2 activate sawtooth generator 14. The sawtooth waveform has a frequency equalling the disk revolution and an amplitude corresponding to the pitch of helical track 1. Summing circuit 13 combines the sawtooth waveform of generator 14 with the staircase waveform from CAR to a straight ramp signal, which is fed to the voice-coil drive contr...