Asynchronous peak detection of information embedded within PRML

Details Asynchronous peak detection of information embedded within PRML Asynchronous peak detection of information embedded within PRML

1992-08-27

1994-06-14

Hajec, Donald

Dynamic magnetic information storage or retrieval

General processing of a digital signal

Head amplifier circuit

360 51, 360 65, G11B 509, G11B 5035

Patent

active

053215591

ABSTRACT:
A digital peak detection circuit asynchronously detects embedded overhead information such as servo or sync pattern data within a PR4,ML synchronous data detection channel of a magnetic disk drive. The channel includes an analog to digital converter clocked by a data clock operating asynchronously with respect to playback of the embedded overhead information in the channel for converting an analog data stream into raw data samples, and an adaptive digital FIR filter for conditioning the raw data samples into conditioned data samples in accordance with programmable filter coefficients. The digital peak detection circuit includes a filter adaptation circuit for programming the digital FIR filter to a bandwidth characteristic selected for the embedded overhead information, a plurality of tapped clock delays each connected in tandem to receive and progressively by a period related to said data clock to delay conditioned data samples of the embedded overhead information, a first comparison logic array connected to predetermined taps of said tapped data clock period delays for comparing said conditioned data samples of the embedded overhead information at said taps and for generating a first logical condition therefrom, a second comparison logic array connected to a predetermined tap of said tapped clock delay means and to a threshold-providing circuit, for comparing the conditioned data samples of the embedded overhead information at the taps with threshold values provided by the threshold-providing circuit and for generating a second logical condition therefrom, and a digital combining circuit for combining the first logical condition and the second logical condition in order to detect and put out the embedded overhead information. A fault tolerant sync pattern detection method and apparatus is also disclosed.

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