GRAY CODE DECODING CIRCUIT OF A HARD DISK DRIVE, SPECIALLY WITH REGARDS TO MINIMIZING AN ERROR CAUSED BY JITTERS OF A TIMING SHIFT AND A SPINDLE MOTOR, TO NORMALLY DECODE A GRAY CODE

摘要

PURPOSE: A gray code decoding circuit of a hard disk drive is provided to reduce a length of gray code patterns, and to minimize an error caused by jitters of a timing shift and a spindle motor, thereby normally decoding a gray code. CONSTITUTION: A window enable signal generator(18) generates a window enable signal for decoding a gray code, and outputs the enable signal. The first gray synchronous window generator(22) generates a window signal for detecting the first synchronous signal of a gray code section, and outputs the signal. A gray code and synchronization extractor(24) generates a synchronous detection signal, decodes encoded read data inputted within a gray data window section enabled by the synchronous detection signal, and extracts gray data. Gray data window generators(26,28,30,32) generate gray data window signals for sequentially detecting gray data bits, and output the generated signals. The second gray synchronous window generator(34) generates a window signal for detecting the second synchronous signal, and outputs the signal to the extractor(24). A gray synchronous counter(20) counts the synchronous detection signal, and disables the window enable signal generator(18) when all gray synchronous bits are detected.