Magnetic disk drive including a data discrimination apparatus capable of correcting signal waveform distortion due to intersymbol interference

摘要

A data discrimination apparatus which is capable of correcting a decrease in amplitude of a signal to be data discriminated by a correction value so as to correct the bit itself which was used as a target bit to determine the correction value. A decision circuit preliminarily classifies an equalizer output into symbols "0" and "1" to obtain a run length of the symbol "0" with respect to a given symbol "1" (the target bit). A correction value generating circuit includes a memory device which contains correction values in correspondence with all the possible values of the run length, and outputs one of the correction values out of the memory device in response to an output from the decision circuit. A delay circuit delays the equalizer output by a time which is required until the correction value is output. An operation circuit adds the selected correction value to the delayed equalizer output, to correct the same. The thus corrected equalizer output is data discriminated in a data discrimination circuit, with a lowered error rate owing to the correction.