Adaptec, Inc.

Fred A Kool

John S Packer

Nicholas S Assouad

Write and read processes for a disk drive handle data and overhead fields in a data frame that extends between two servo sectors on a disk. A write process fills a buffer with both data values and overhead values sufficient to fill a data frame and then writes the entire data frame based on the values in the buffer. Accordingly, activation of a separate formatting circuit is not required as those fields are written, and the write operation does not require sector pulses to control the timing for writing individual data sectors in the data frame. The overhead fields written include VFO fields and data synchronization fields. The read process uses timing signals derived from detection of servo sectors and data synchronization fields but otherwise sequentially reads data and overhead fields and transfers those fields to a buffer. The data in a requested sector can be separated from overhead information and data of other sectors in the buffer, when the disk drive outputs the requested data.

Data frame write and read processes

A headerless hard disk architecture includes tracks that are grouped into logical zones and physical zones. The physical zones contains tracks which have similar data density and rotational velocity and therefore would have the same track format on a defect-free media. The logical zones are subdivisions of the physical zones and contain tracks similarly affected by defects on a media. A single track format for all of the tracks in a logical zone accounts for defects. A first data structure stored in a data buffer indicates boundaries of data sectors as defined by the track formats for the logical zones. A second data structure in the data buffer indicates which of the data sectors contain defects not accounted for by track formats. A disk controller uses a combination of information from the first and second data structures to identify logical data sectors requested for a data transfer.

Logical and physical zones for management of defects in a headerless

A disk controller for headerless disk drive system contains an EOS counter which increments each time a read/write head passes a servo sector. Control words in a data buffer of the disk drive system and event-counts in registers of the disk controller indicate sizes and relative positions of frame fields between the servo sectors. The disk controller decodes control words from a data buffer to determine which fields are in the data frames and determine event-counts for the frame fields. The position of read/write heads in a data frame is then determined by counting pulses of a read or write clock where counting to an event-count identifies a boundary of a frame field. The disk controller synchronizes with the media at EOS pulses and data synchronization fields and otherwise relies on the event-counts and the read or write clock signal. No sector pulses are required because data segments are identified by timing relative to EOS pulses. Assertion of a read gate during a read can be delayed to ensure that variation in the timing of assertion and detection of EOS pulses does not cause a read gate to be asserted before the read/write head reach a data segment.

Programmable data transfer without sector pulses in a headerless disk

A disk controller for headerless disk drive system contains a decoder which decodes control words from a data buffer and counts pulses of a byte clock to identify the boundaries of requested data sectors in data frames. To select the control words which correspond to the position of a read/write head relative to media containing the data, the disk controller also contains a programmable alignment processor and an EOS counter that increments in response to EOS pulses generate as the read/write head passes servo sectors. The EOS counter indicates the position of the read/write head by indicating a data frame over which the head is positioned. The alignment processor scans the control words to locate the control word corresponding the data frame indicated by the EOS counter. During the scanning, the alignment processor also aligns logical and physical data sector counters to the position of the read/write head. The disk controller uses the aligned values and begins decoding the control words and controlling data transfer.

Hardware alignment in a headerless disk drive architecture

A disk drive system for a constant density recording (CDR) format disk has a microprocessor which generates CDR words from split values stored in a ROM. The CDR words indicate how embedded servo sectors split data sectors into data fields. In one embodiment, during a seek to a track, the microprocessor stores in a data buffer the CDR words for requested data sectors on the track. Alternatively, track CDR tables are stored in the data buffer during start-up and altered during a seek. A disk sequencer reads CDR words from the data buffer into a FIFO buffer as required to locate splits in data sectors. Alternatively the microprocessor writes the CDR word directly into the FIFO buffer. Typically, the microprocessor writes CDR words for a data frame, into the FIFO buffer, during a servo burst preceding the data frame, but the microprocessor can wait two or more servo bursts before writing CDR words for two or more data frames. Data transfer for each requested data sector is initiated by a sector pulse. The CDR words can identify requested data sectors. Otherwise, the microprocessor suppresses sector pulses for unwanted data sectors or qualifies sector pulses with a signal that confirms a data sector is requested.

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Aptos, CA, United States of America

Fred A Kool