Browse Prior Art Database

Proposed Pulse Width Modulation Sector Mark

IP.com Disclosure Number: IPCOM000111208D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 116K

Publishing Venue

IBM

Related People

Belser, KA: AUTHOR

Abstract

The purpose of this paper is to describe a sector mark that is adequate for use with Pulse Width Modulation (PWM) recorded data. It is intended that this sector mark be added to the sector format given in ECMA/TC31/92/29. Requirements of the Sector Mark - The occurrence of the sector mark tells the drive when to start a timing sequence that controls the fast sync of the PLO and the ROM to MO switch. The sector mark must be asynchronously decoded because the frequency of the clock used to decode the sector mark is nominally correct but cannot be assumed to be correctly phased relative to the sector mark features. Further, in the case of zone recorded media, it is possible, say for a seek that misses the desired track by a few tracks, for the sector mark of an adjacent zone to be decoded by the clock for the desired zone.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Proposed Pulse Width Modulation Sector Mark

      The purpose of this paper is to describe a sector mark that is
adequate for use with Pulse Width Modulation (PWM) recorded data.  It
is intended that this sector mark be added to the sector format given
in ECMA/TC31/92/29.  Requirements of the Sector Mark - The occurrence
of the sector mark tells the drive when to start a timing sequence
that controls the fast sync of the PLO and the ROM to MO switch.  The
sector mark must be asynchronously decoded because the frequency of
the clock used to decode the sector mark is nominally correct but
cannot be assumed to be correctly phased relative to the sector mark
features.  Further, in the case of zone recorded media, it is
possible, say for a seek that misses the desired track by a few
tracks, for the sector mark of an adjacent zone to be decoded by the
clock for the desired zone.  The worst case error in frequency is
31/30 or 3.33 percent high when the 28th zone sector mark is decoded
with the 29th zone's clock.  The sector mark must be defined such
that the sector mark can be read with such a frequency error.
Further, it is desirable for the sector mark to be different on
adjacent zones such that the system know immediately that it is in
wrong zone.  The PLO may not be able to lock onto the data in the
adjacent zone when the nominal clock frequency is in error.

      The requirements for the sector mark are as follows.  Note that
the clock period is referred to as a Channel Code Bit time or CCB
time.

o   The sector mark must be asynchronously decoded with a clock that
    can vary 3.33 percent from its nominal value in order to
    accommodate adjacent zone sector mark detection.  The channel
    code bit length is assumed to be 0.376 um which corresponds to 45
    kbpi.  Thus, a 30 CCB run can result in a 1 CCB length error
    due to frequency variation.

o   The sector mark encoding(s) must be uniquely decodable relative
    to other sector marks, header information, and user data.  In
    this case (1,7) encoded PWM data is used so that the longest
    marks and spaces are 8 channel code bits times.

o   The sector mark should be robust enough to tolerate at least one
    pit type defect that is 12 CCBs (one byte) long.

o   There must be at least two sector mark types to encode even and
    odd zones in...