CIRCUIT FOR DETECTING SAM PULSES OF HARD DISK DRIVE

摘要

PURPOSE: A circuit for detecting SAM pulses of a hard disk drive is provided to reduce an error of an HDD(Hard Disk Drive) by making a new virtual SAM. CONSTITUTION: First and second counters(601,611) count clocks of clock terminals. A latch circuit(603) latches output of the first counter according to a signal of a normal SAM(Servo Address Mark) detection signal terminal(Q1). First and second storing units(604,624) store plus/minus value of the stored G-SAM according to output of the latch circuit. First and second comparators(605,607) compare the count value of the second counter with the output of the first and second storing units. A J and K flip-flop(608) latches the output of the first and second comparators for generating a window signal. A NOR gate(609) executes NOR operation with an inversion signal of the window signal and the signal of the normal SAM detection signal terminal. A D flip-flop(610) latches the output of the NOR gate according to a signal from an output terminal of the J and K flip-flop. A G-SAM storing unit(612) stores the G-SAM. A third counter(613) counts clocks of another clock terminal. A third comparator(614) compares the output of the G-SAM storing unit with the output of the third counter. A three-state buffer(615) generates SAM pulses by the output of the D flip-flop.