Browse Prior Art Database

Phase Lock Loop Freeze for Hard Disk Drive

IP.com Disclosure Number: IPCOM000116970D
Original Publication Date: 1995-Dec-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Numata, T: AUTHOR [+3]

Abstract

Disclosed is a hard disk drive which has phase lock loop freeze functions; which determine the error location with the read/write channel signals.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Phase Lock Loop Freeze for Hard Disk Drive

      Disclosed is a hard disk drive which has phase lock loop freeze
functions; which determine the error location with the read/write
channel signals.

      If there are large missing bits and/or large extra bits
location, Phase Lock Loop (PLL) does not work correctly and causes
burst error.  This method is to apply PLL Freeze signal into the
read/write channel where the error location was detected by previous
Error Recovery Procedure (ERP).

      The Figure shows one of the implementations of this algorithm.
If there are large missing bits, Channel pulse detector output (PDRD)
has no signal location (2).  Hard Disk Controller (HDC) is counting
the low period and if it exceeds two bytes length, which cannot exist
in the normal Run length, HDC enables the PLL freeze bits and saves
the location onto the memory (3).  Micro Code can apply PLL freeze
signal into the read/write channel (4), which may have data error.

      The benefit of this method is minimizing the disturbance of
the read back signal which causes the malfunction of PLL.