Accumulating read channel performance data

Details Accumulating read channel performance data Accumulating read channel performance data

2000-04-17

2003-10-21

Hudspeth, David (Department: 2651)

Dynamic magnetic information storage or retrieval

Monitoring or testing the progress of recording

C360S053000

Reexamination Certificate

active

06636372

ABSTRACT:

TECHNICAL FIELD
This invention relates to systems and methods for accumulating data relating to the performance of one or more components of a read channel.
BACKGROUND
In a magnetic disk storage system, a read channel extracts information stored on a magnetic disk and delivers that information to a host system (e.g., a computer). The magnetic disk is formatted with a plurality of concentric data tracks, each of which is configured to store a fixed quantity of data in the form of magnetic transitions on the disk surface. A spindle motor rotates the magnetic disk and a magnetic transducer positioned adjacent to the disk senses the magnetic transitions on the disk surface and produces an input read signal corresponding to the recorded data. The read channel includes a plurality of components for reconstructing the recorded data from the input read signal received from the transducer. Sampled amplitude read channels include components (e.g., a digital wave shaping circuit and a digital filter) for equalizing the input read signal into a predetermined partial response (e.g., PR4 or EPR4) that enables the output of the read channel to be approximated as a linear combination of time delayed pulses modulated by a binary sequence.
The operation of a sampled amplitude read channel may be optimized by adjusting one or more of the read channel components that equalize the input read signal. Programmable digital read channels enable technicians to program read channel components to improve the data detection capability of the channels and to optimize the read channels for different disk drive systems. In order to optimize a read channel, the technician must monitor the performance of the channel under prescribed test conditions. For example, in one optimization technique, a known test pattern is written to a sector of a magnetic disk and compared to the pattern detected by the read channel. Such a comparison may be used to compute one or more statistical performance measures (e.g., mean of squared sample errors) characteristic of the current read channel configuration. In order to perform a meaningful statistical analysis, however, a sufficient quantity of data must be collected. Various techniques (e.g., introducing noise into the read channel) have been proposed to reduce the amount of data needed to perform statistical analyses on the read channel output. In addition, programmable channel quality monitors have been developed to help accumulate test data for calibrating a read channel. For example, U.S. Pat. No. 5,987,634 describes a channel quality circuit in a sampled amplitude read channel. The channel quality circuit generates a test data pattern that is written to a sector of a formatted magnetic storage disk. As the test pattern is read from the storage disk sector, the channel quality circuit accumulates performance data from the read channel components. Gating logic is programmed to accumulate only the particular performance data of interest.
SUMMARY OF THE INVENTION
The invention features systems and methods for accumulating performance data from a read channel configured to extract data symbols from a magnetic medium having a plurality of formatted data sectors. In accordance with this inventive scheme, a programmable channel quality monitor is operable to accumulate performance data corresponding to a recorded test data sequence spanning two or more data sectors of the magnetic medium.
Embodiments may include one or more of the following features.
The channel quality monitor preferably is programmable to delay the accumulation of performance data during a delay period corresponding to a programmed number of data symbols following a received trigger signal. The channel quality monitor may be programmable to begin the delay period after a sync mark signal is received, or after a read gate signal is received. The channel quality monitor preferably includes a delay counter configured to provide an end-of-delay signal after the programmed delay period has expired.
The channel quality monitor preferably is programmable to accumulate a programmed quantity of performance data. The channel quality monitor may be programmable to accumulate performance data corresponding to data symbols from multiple data sectors of the magnetic medium. The channel quality monitor preferably includes a measurement counter configured to provide an end-of-measurement signal after the programmed quantity of performance data has been accumlated. The channel quality monitor may be programmable to accumulate performance data corresponding selected data symbols of each magnetic medium sector from which data is accumulated. The accumulation of performance data may be suspended during a delay period corresponding to a programmable number of data symbols at the beginning of each sector from which data is accumulated.
In one aspect, the invention features a disk drive system. The system includes at least one magnetic storage disk having a plurality of formatted data sectors. The system also includes at least one transducer configured to extract an encoded data signal from the magnetic storage disk. The system has a read channel configured to extract encoded data symbols from the encoded data signal. The system also has a programmable channel quality monitor operable to accumulate performance data corresponding to a recorded test data sequence spanning two or more data sectors of the magnetic medium.
In another aspect, the invention features a method of accumulating performance data from a read channel configured to extract data symbols from a magnetic medium having a plurality of formatted data sectors. In accordance with this inventive method, an original test data pattern is written to multiple data sectors of the magnetic medium. The original test pattern is read from the multiple data sectors of the magnetic medium to produce a readback test pattern. In this method, performance data relating to a comparison of the original test pattern and the readback test pattern is accumulated.
A total number of sectors in error preferably is determined. A sector may be determined to be in error if a single byte in the sector is in error, or if more than one byte in the sector is in error.
Advantages of the invention include that a disk drive technician may readily collect a large quantity of performance data, because the test data patterns written to the magnetic medium may span multiple data sectors. In addition, the disk drive technician may perform a wide variety of different performance tests with a test data pattern stored in one or more sectors of the magnetic medium (e.g., a sector error test that spans a plurality of sectors).


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