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Browse Prior Art Database

Clock Track Write by using Synthesizer

IP.com Disclosure Number: IPCOM000113272D
Original Publication Date: 1994-Aug-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Suzuki, H: AUTHOR [+3]

Abstract

Disclosed is system for clock track writer by using synthesizer. Before servo track writing of Hard Disk Drive (HDD), clock track must be written on disk surface by clock head. Clock track count per 1 revolution is specified strictly. This system achieve clock track writer by using synthesizer.

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Clock Track Write by using Synthesizer

      Disclosed is system for clock track writer by using
synthesizer.  Before servo track writing of Hard Disk Drive (HDD),
clock track must be written on disk surface by clock head.  Clock
track count per 1 revolution is specified strictly.  This system
achieve clock track writer by using synthesizer.

      The Figure shows main construction of this system.  This system
composed by synthesizer, frequency change counter and timer.

1.  Write index pulse by product head.

2.  Measure time interval of index to index (1 revolution time : t)

3.  Calculate ideal synthesizer frequency (fi) from specified clock
    count (N) and 1 revolution time (t) as follows.
    fi = N (clock count) / t (1 revolution time)

4.  Achievable frequency which is two nearest value to ideal
    synthesizer frequency is calculated as f1 (nearest value but
    lower than ideal value) and f2 (nearest value but higher than
    ideal value).

5.  Calculate frequency change point (Nc) as follows.
    ( Nc / f1 ) +(( N - Nc) / f2 ) = t

      Purpose of frequency change counter is to change synthesizer
frequency at proper point to meet 1 revolution clock count to 1
revolution time.

      The above is open loop control, but closed loop system is
possible by detecting phase error between 1 revolution time and 1
revolution clock count time.  In this case, frequency change counter
is changed by phase error signal.