Dynamic magnetic information storage or retrieval – General processing of a digital signal – Address coding
Patent
1996-02-08
1998-05-26
Sniezek, Andrew L.
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Address coding
360 7814, G11B 509
Patent
active
057575673
ABSTRACT:
A gray code is provided for use with disk servo track identification encodement that preserves the gray code property of only a single digit changing state between two numbers in the code sequence and also preserves magnetization between code numbers while only requiring a single bit for encoding each code value by recording a single pad bit before the gray code bits. By proper selection of the sign of the pad bit and the gray code numbering sequence, the gray code encodement scheme uses n+1 code bits for an n-bit gray code. The efficiency of the gray code encodement can be enhanced by splitting the track identification number to be recorded into multiple fields and then recording only the low order bits sufficient to identify a track within the maximum estimated error of the servo head on every track and otherwise alternating the high and low middle order bit fields with the low order bit field. A run-length limiting feature also can be provided. One way is for the encoded bits to be broken into fields so that only two are written in each sector. The two fields are concatenated and encoded so that the length of the field is shorter than the run-length limit. Alternatively, the code sequence can be obtained as a subsequence of a larger sequence. This subsequence then obeys the run-length limit.
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M. Kisaka, et al., "Improved Gray Code Pattern on a Hard Disk", IBM Technical Disclosure Bulletin, vol. 35, No. 4B, pp. 373-374, Sep. 1992.
H. E. Korth, "Sectored Servo Headers for Optical Storage Devices", IBM Technical Disclosure Bulletin, vol. 31, vol. 10, pp. 256-257, Mar. 1989.
Hetzler Steven Robert
Serrano Louis Joseph
International Business Machines - Corporation
Sniezek Andrew L.
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